Boston Marathon bombing

== April 18–19 shootings and manhunt ==
{{Infobox civilian attack
| title            = Tsarnaev brothers shootings and manhunt
| image            = File:Two suspects wanted by the FBI for the bombing.jpg
| image_size       = 250px
| alt              = 
| caption          = Security camera images of Tamerlan Tsarnaev (front) and Dzhokhar Tsarnaev just prior to the bombings<ref name="AutoLC-55" />
| map              = 
| map_size         = 
| map_alt          = 
| map_caption      = 
| location         = '''Shooting:''' Corner of Vassar Street and Main Street in [[Cambridge, Massachusetts]]<ref>{{cite web|title=He loved us, and we loved him|date=April 19, 2013 |url=http://web.mit.edu/newsoffice/2013/obit-officer-sean-collier-0419.html|publisher=MIT|access-date= April 11, 2015}}</ref><br />'''Firefight and manhunt:''' [[Watertown, Massachusetts]]
| target           = 
| date             = {{Nowrap|'''Shooting:'''}} {{Nowrap|April 18, 2013}}, {{Nowrap|10:25{{nbsp}}p.m.}}<br /> {{Nowrap|'''Firefight and manhunt:'''}} {{Nowrap|April 19, 2013,}} {{Nowrap|12:30{{nbsp}}a.m.}} – {{Nowrap|8:42{{nbsp}}p.m.}}
| type             = {{Flatlist|Shooting, vehicle ramming, [[Lone wolf (terrorism)|lone wolf terrorism]]<ref name="Berman" />}}
| fatalities       = 3 (including Tamerlan Tsarnaev and a victim who died in 2014<ref name="Simmonds" />)
| injuries         = 16 (via gunfire)
| victim           = 
| perp             = 
| perpetrators     = * Dzhokhar Tsarnaev (sentenced to death)
* Tamerlan Tsarnaev (deceased)
| perpetrator      = 
| perps            = 
| susperp          = 
| weapons          = * '''Shooting:''' [[9mm]] [[Ruger P series|Ruger P95]] semi-automatic pistol
* '''Firefight:'''
** [[Improvised explosive device]]s
** 9mm Ruger P95 semi-automatic pistol
** Stolen [[Mercedes-Benz M-Class]] SUV
| numparts         = 
| numpart          = 
| dfens            = 
| dfen             = 
| footage          = 
| motive           = [[Firearm]]s [[Theft|theft]] (murder of MIT officer)<br />[[Resisting arrest|Evading arrest]] (Watertown shootout)
}}

=== Release of suspect photos ===
[[Jeff Bauman]] was immediately adjacent to one of the bombs and lost both legs; he wrote while in the hospital: "Bag, saw the guy, looked right at me".<ref name="Bauman evidence" /> He later gave a detailed description of the suspects, which enabled images of them to be identified and circulated quickly.<ref name="Bauman evidence" /><ref name="AutoLC-53" /><ref name="AutoLC-54" />

At 5:00{{nbsp}}p.m. on April 18, three days after the bombing, the FBI released images of two suspects carrying backpacks, asking the public's help in identifying them.<ref name="FBI18AprSuspectPics" /><ref name="FBI plea" /> The FBI said that they were doing this in part to limit harm to people wrongly identified by news reports and on social media.<ref name="AutoLC-175" />
As seen on video, the suspects stayed to observe the chaos after the explosions, then walked away casually. The public sent authorities a deluge of photographs and videos.<ref name="FBI plea" /> The FBI-released images depicted Dzhokhar and Tamerlan Tsarnaev.<ref name="relaxed">Yashwant Raj, [http://www.hindustantimes.com/News-Feed/Chunk-HT-UI-WorldSectionPage-BostonBlast/Boston-bomber-partied-with-friends-after-attack/Article1-1048258.aspx "Boston Bomber Partied with Friends after Attack"] {{webarchive|url=https://web.archive.org/web/20150626150311/http://www.hindustantimes.com/News-Feed/Chunk-HT-UI-WorldSectionPage-BostonBlast/Boston-bomber-partied-with-friends-after-attack/Article1-1048258.aspx |date=June 26, 2015 }}, ''[[Hindustan Times]]'', April 22, 2013.</ref>

=== MIT shooting and carjacking ===
[[File:Scenes and approximate times of events of April 18-19.jpg|thumb|upright=1.8|left|Scenes and approximate times of events of April 18–19]]
Hours after the FBI released photos of the two suspects in the bombing, Tamerlan and Dzhokhar Tsarnaev visited their family's apartment in Cambridge. There, they obtained five improvised explosive devices (IEDs), ammunition, a semiautomatic handgun, and a machete. The two brothers then drove to the Massachusetts Institute of Technology.<ref name="auto1"/>

On April 18, 2013 at 10:25&nbsp;p.m., the Tsarnaev brothers ambushed and shot Sean A. Collier of the [[Massachusetts Institute of Technology Police Department]] six times.<ref name="admits" /><ref name="auto1"/> The two brothers were attempting to steal Collier's [[Smith & Wesson M&P|Smith & Wesson M&P45]] sidearm, which they could not free from his holster because of its security retention system.<ref>{{cite news|date=April 23, 2013|title=Police believe Tsarnaev brothers killed officer for his gun|work=CBS News|url=https://www.cbsnews.com/news/police-believe-tsarnaev-brothers-killed-officer-for-his-gun/|access-date=April 11, 2015}}</ref> Collier, aged 27, was seated in his police car near [[Ray and Maria Stata Center|Building 32]] on the Massachusetts Institute of Technology campus.<ref name="NY Times Standoff" /><ref name="lowery" /> He died shortly after the shooting.<ref name="NY Times Standoff" /><ref name="AutoLC-58" />

{{multiple image
 | width = 200px
 | align = right
 | direction = vertical
 | image1 = RIP Officer Sean Collier (9887748094).jpg
 | caption1 = Temporary memorial to Collier
 | alt1 =
 | image2 = Sean-collier-memorial-service 5541156712 o.jpg
 | caption2 = Police officers carrying the coffin of Collier at an April 24 service
 | alt2 =
 | image3 = Sean-collier-memorial-service 5608419026 o.jpg
 | caption3 = Vice President [[Joe Biden]] speaks with Governor Deval Patrick at the April 24 service for Collier
 | alt3 =
}}

The brothers then [[carjacked]] a [[Mercedes-Benz M-Class]] [[SUV]] in the [[Allston-Brighton]] neighborhood of Boston. Tamerlan took the owner, Chinese national Dun "Danny" Meng<ref>{{cite news|url=https://www.cbsnews.com/news/boston-marathon-bombing-jurors-see-dramatic-video-of-carjack-victims-escape/|title=Boston bombing jurors see dramatic video of carjack victim's escape|agency=CBS/[[Associated Press|AP]] | work=[[CBS News]] | date=March 12, 2015|access-date=March 12, 2015}}</ref> ({{zh|c=孟盾}}),<ref>Chinese name from: {{cite news|url=http://ny.uschinapress.com/weekends/2017/01-13/111620.html|title=《爱国者日》上映 再现波马爆炸案 留学生孟盾事迹搬...|newspaper=[[The China Press]]|date=January 13, 2017|access-date=September 22, 2018|archive-date=September 21, 2018|archive-url=https://web.archive.org/web/20180921191256/http://ny.uschinapress.com/weekends/2017/01-13/111620.html|url-status=dead}}</ref> hostage and told him that he was responsible for the Boston bombing and for shooting Collier.<ref name="NY Times Standoff" /> Dzhokhar followed them in their green [[Honda Civic]], later joining them in the Mercedes-Benz. Interrogation later revealed that the brothers "decided spontaneously" that they wanted to go to New York and bomb [[Times Square]].<ref name=Gorman />

The Tsarnaev brothers forced Meng to use his ATM cards to obtain $800 in cash (equivalent to ${{Inflation|US|800|2013|fmt=c}} in {{Inflation/year|US}}).<ref name="AutoLC-60" /><ref name="WashPost04192013" /> They transferred objects to the Mercedes-Benz and one brother followed it in their Civic,<ref name="wsjdetails" /> for which an [[all-points bulletin]] was issued. The Tsarnaev brothers then drove to a [[Shell Oil Company|Shell]] gas station on Memorial Drive in Cambridge to fill up for the long ride to Times Square to set off more explosives. But while Dzhokhar went inside to pay for junk food, Meng, fearing that the suspects would harm him during the long drive, escaped from the Mercedes and ran across the street to the [[Mobil]] gas station, asking the clerk to call 911.<ref name="AutoLC-62" /><ref name="AutoZ2-11" /> His cell phone remained in the vehicle, allowing the police to [[Mobile phone tracking|focus their search]] on Watertown.<ref name="cnnpol" />
<!-- Map hidden pending its updating to reflect the actual, correct locations of where things happened. Hijacking of SUV did not happen in East Cambridge. -->
<!-- {{Wide image|Boston marathon event map.png|900px|Map of events related to the Boston Marathon bombing (1) and subsequent manhunt (times approximate)<br />2) April 18, 10:30{{nbsp}}p.m. – MIT police officer Sean Collier shot and killed<br />3) April 18, 11:00{{nbsp}}p.m. – SUV hijacked<br />4) April 18, shortly thereafter – SUV driver escaped unharmed<br />5) April 18, 11:18{{nbsp}}p.m. – Surveillance photos identify brothers at an ATM<br />6) April 19, 1:00{{nbsp}}a.m. – Gunfire opens up on Laurel St. in Watertown between police and suspects. Tamerlan Tsarnaev is critically injured in the incident and later reported dead. Dzhokhar Tsarnaev escapes<br />7) April 19, 7:00{{nbsp}}p.m. – More gunfire breaks out in Watertown, on Franklin St.; Dzhokhar is found hiding in a stored boat and taken into custody around 8:45{{nbsp}}p.m. EDT}} -->

=== Watertown shootout ===
Shortly after midnight on April 19, Watertown police officer Joseph Reynolds identified the brothers in the [[Honda]] and the stolen Mercedes after overhearing radio traffic that the vehicle was "pinged" by Cambridge officers on Dexter Avenue in Watertown. Reynolds followed the vehicle while waiting for additional units to perform a high-risk traffic stop when the suspect vehicles both turned onto Laurel Street and stopped at the intersection of Laurel and Dexter.{{cn|date=December 2023}}

Tamerlan Tsarnaev stepped out of the Mercedes and immediately opened fire on Officer Reynolds and Sergeant John MacLellan, who both returned fire and requested emergency assistance over their radios. A gun battle ensued between Tsarnaev, the aforementioned officers, and additional officers responding to the "shots fired" radio transmissions from Reynolds and MacLellan in the 100 block of Laurel St.<ref name="NY Times Standoff" /><ref name="captured" /><ref name="Watertown firefight, Globe" /> An estimated 200 to 300 shots were fired. The suspects shot 56 times, detonated at least one pressure cooker bomb, and threw five "crude grenades", three of which exploded.<ref name="Watertown firefight, Globe" /><ref name="AutoLC-65" />

The agencies involved in the nearly seven-minute shootout included the Watertown Police Department, [[Cambridge Police Department]], [[Boston Police Department]], [[Massachusetts State Police]] (MSP), [[Boston University]] Police Department, and MBTA Transit Police Department. Most of the officers involved were equipped by their respective agencies with either the [[Glock 22]] or [[Glock 23]] [[.40 S&W]]-caliber pistols. MSP troopers were armed with [[Smith & Wesson M&P|Smith & Wesson M&P45]] pistols chambered in [[.45 ACP]]; this led investigators to match the [[9mm]] casings and projectiles found at the scene to the suspects' 9mm [[Ruger P95]] pistol.

According to Watertown Police Chief Edward Deveau, the brothers had an "arsenal of guns".<ref name="Tucson Citizen" /> Tamerlan eventually ran out of ammunition and threw his empty Ruger pistol at Watertown PD Sergeant Jeffrey Pugliese, who subsequently tackled him with assistance from Sergeant MacLellan.<ref name="DeWitt2013">{{cite news|last1=DeWitt|first1=Vincent|title=Watertown Mass. Police describe takedown of Boston Marathon bombers|url=https://nypost.com/2013/07/08/exclusive-watertown-mass-police-describe-takedown-of-boston-marathon-bombers/|access-date=March 26, 2016|work=New York Post|date=July 8, 2013}}</ref><ref name="Smith2016">{{cite news|last1=Smith|first1=Tovia|title=Filming For Marathon Bombing Movie Stirs Emotions In Boston|url=https://www.npr.org/2016/03/25/471755112/-its-going-to-trigger-lot-of-ptsd-boston-prepares-for-marathon-bombing-film|access-date=March 26, 2016|work=NPR|date=March 25, 2016}}</ref>

Tamerlan's younger brother Dzhokhar then drove the stolen SUV toward Tamerlan and the police, who unsuccessfully tried to drag Tamerlan out of the car's path and handcuff him;<ref name="DeWitt2013" /><ref name="Smith2016" /> the car ran over Tamerlan and dragged him a short distance down the street, narrowly missing the Watertown officers. Watertown Sgt. MacLellan later stated that the younger brother had thought they were doing [[CPR]] on another officer and tried to run them over.<ref name="NY Times Standoff"/><ref name="DeWitt2013"/><ref name="AutoLC-66"/><ref name="AutoLC-67"/> Dzhokhar abandoned the car half a mile away and fled on foot.<ref name="NY Times Standoff"/><ref name="cnnpol"/><ref name="AutoSQ-1"/><ref name="AutoLC-71"/> Badly wounded, Tamerlan Tsarnaev was taken into custody and died at 1:35{{nbsp}}a.m. at [[Beth Israel Deaconess Medical Center]].<ref>{{Cite news|last=Bidgood|first=Jess|date=May 4, 2013|title=Autopsy Says Boston Bombing Suspect Died of Gunshot Wounds and Blunt Trauma|language=en-US|work=The New York Times|url=https://www.nytimes.com/2013/05/05/us/autopsy-says-boston-bombing-suspect-died-of-gunshot-wounds-and-blunt-trauma.html|access-date=September 7, 2020|issn=0362-4331}}</ref>

[[Massachusetts Bay Transportation Authority]] Police Officer Richard H. Donohue Jr.<ref name="AutoLC-28"/> was critically wounded in the leg<ref name="Auto9P-2"/> in crossfire from other officers shooting at the fleeing vehicle, but survived. Reports revealed that his gunshot wound severed his [[femoral artery]], and he nearly died. Fast-acting efforts by his fellow officers and medical personnel saved his life.<ref>{{cite news |date=April 15, 2014 |title=Donohue Talks Miracle Survival On Toucher & Rich: 'I Don't Have An Explanation For It' |url=http://boston.cbslocal.com/2014/04/15/dic-donohue-talks-miracle-survival-on-toucher-and-rich/ |newspaper=CBS Boston }}</ref> Boston Police Department officer Dennis Simmonds was injured by a hand grenade and died on April 10, 2014.<ref name=Simmonds/> Fifteen other officers were also injured.<ref name="captured" /> A later report by Harvard Kennedy School's Program on Crisis Leadership concluded that lack of coordination among police agencies had put the public at excessive risk during the shootout.<ref>{{cite news |last1=Schworm |first1=Peter |last2=Cramer |first2=Maria |date=April 30, 2013 |title=Harvard report praises response to Marathon bombings |url=https://www.bostonglobe.com/metro/2014/04/02/harvard-university-report-draws-lessons-from-marathon-bombings/qhXQcxi6jCxQqQnojtC3dP/story.html |newspaper=[[The Boston Globe]] }}</ref>

Only one firearm, Tsarnaev's Ruger P95, was recovered at the scene. That firearm was found to have a defaced serial number.<ref name="AutoLC-68"/><ref name="ABC24Apr">{{cite news | first1 = Jack | last1 = Date | first2 = Matthew |last2 = Mosk | title = Single Gun Recovered From Accused Bombers | date = April 24, 2013 | publisher = ABC News | url = https://abcnews.go.com/Blotter/single-gun-recovered-accused-boston-bombers/story?id=19028841 | work = ABC The Blotter | access-date = May 16, 2013}}</ref>

=== Further investigation and post-shootout search for Dzhokhar Tsarnaev ===
{{further|Dzhokhar Tsarnaev|Tamerlan Tsarnaev}}
<!-- Please do not add details on the lives of the suspects, unless it is connected to the bombing by a reliable source. See discussion on the talk page. -->
Records on the Honda left at the Watertown shootout scene identified the bombers<ref name="Honda Civic Evidence">{{cite web|url=http://investigations.nbcnews.com/_news/2013/05/01/17991679-green-honda-could-prove-crucial-if-tsarnaev-charged-in-mit-officers-killing?lite |title=Green Honda could prove crucial if Tsarnaev charged in MIT officer's killing – Investigations |publisher=Investigations.nbcnews.com |date=August 29, 2010 |access-date=July 24, 2013}}</ref> Tamerlan and Dzhokhar "Jahar" Tsarnaev.<ref name="Slate pronunciation" /><ref name="AtlanticWire04192013" /> The FBI released additional photos of the two during the Watertown incident.<ref name="Philippe Naughton" /> Early on April 19, investigators released the name and photo of Dzhokhar Tsarnaev to the public.<ref name="auto1"/> In addition, Watertown residents received automated calls asking them to stay indoors.<ref name="AutoLC-74" /> That same morning Governor Patrick asked residents of Watertown and adjacent cities and towns<ref>Boston, [[Belmont, Massachusetts|Belmont]], [[Brookline, Massachusetts|Brookline]], [[Cambridge, Massachusetts|Cambridge]], [[Newton, Massachusetts|Newton]], and [[Waltham, Massachusetts|Waltham]]</ref><ref name="AutoLC-75" /><ref name=cisomerville /> to "[[shelter in place]]".<ref name=nationRawlings /> [[Somerville, Massachusetts|Somerville]] residents also received automated calls instructing them to shelter in place.<ref name="AutoQU-4" /> 

A 20-block area of Watertown was [[Cordon and search|cordoned off]] and residents were told not to leave their homes or answer the door, as officers scoured the area in tactical gear. Helicopters circled the area and [[SWAT]] teams in armored vehicles moved through in formation, with officers going door to door and searching houses.<ref name="AutoLC-76" /> These actions generated discussions about the legality of searching large numbers of houses without a [[search warrant]], with ''[[The Atlantic]]'' stating that this kind of search is legal due to [[exigent circumstance]]s.<ref>{{Cite web |last=Bump |first=Philip |date=2013-04-22 |title=Boston's Door-to-Door Searches Weren't Illegal, Even Though They Looked Bad |url=https://www.theatlantic.com/national/archive/2013/04/boston-door-to-door-searches-legal/316042/ |access-date=2022-09-06 |website=The Atlantic |language=en}}</ref> Agencies on the scene were the FBI; the Bureau of Alcohol, Tobacco, Firearms, and Explosives; Diplomatic Security Service; HSI-ICE; [[National Guard of the United States|the National Guard]]; the Boston, Cambridge, and Watertown Police departments; and the [[Massachusetts State Police]]. The show of force was the first major field test of the interagency task forces created in the wake of the [[September 11 attacks]].<ref name="AutoLC-77" />

The entire [[Massachusetts Bay Transportation Authority|public transit network]] and most Boston taxi services{{Efn|Taxi service was restored before the manhunt ended and transit service resumed.<ref name="AutoQU-5" />}} were suspended, as was [[Amtrak]] service to and from Boston.<ref name="lowery" /><ref name="Logan and Taxis" /> [[Logan International Airport]] remained open under heightened security.<ref name="Logan and Taxis" /> Universities, schools, many businesses, and other facilities were closed as thousands of law enforcement personnel participated in the door-to-door manhunt in Watertown. Others followed up on other leads, including searching the house that the brothers shared in Cambridge, where seven improvised explosive devices were found.<ref>{{cite news|url=http://usnews.nbcnews.com/_news/2013/04/20/17823265-we-got-him-boston-bombing-suspect-captured-alive|title='We got him!': Boston bombing suspect captured alive|last1=Williams|first1=Pete|last2=Esposito|first2=Richard|date=April 8, 2015|work=NBC News|access-date=April 8, 2015|last3=Isikoff|first3=Michael|last4=Connor|first4=Tracy}}</ref>

The brothers' father spoke from his home in [[Makhachkala, Dagestan]], encouraging Dzhokhar to: "Give up. You have a bright future ahead of you. Come home to Russia." He continued, "If they killed him, then all hell would break loose."<ref name="AutoLC-80" /> On television, Dzhokhar's uncle from [[Montgomery Village, Maryland]], pleaded with him to turn himself in.<ref name="AutoLC-81" />

Also on April 19, the FBI, [[West New York]] Police Department, and [[Hudson County, New Jersey|Hudson County]] Sheriff's Department seized computer equipment from the apartment of the Tsarnaevs' sister in West New York, New Jersey.<ref name="AutoLC-52" /> 

[[File:JaharTsarnaev.jpg|thumb|Dzhokhar Tsarnaev at the time of his capture]]
[[File:MissionHillCaptureCelebrations.jpg|thumb|Post-capture celebrations in Boston's student-heavy [[Mission Hill, Boston|Mission Hill]] neighborhood]]

On the evening of April 19, after the shelter-in-place order had been lifted, David Henneberry, a Watertown resident outside the search area, noticed that the tarpaulin was loose on his parked boat.<ref name="AutoLC-83" /><ref name="BBCboat" /> Investigating, he saw a body lying inside the boat in a pool of blood.<ref name="AutoLC-84" /> He contacted the authorities at 6:42 p.m., and they surrounded the boat. A police helicopter verified movement through a [[thermal imaging]] device.<ref name="captured" /><ref name="AutoLC-85" /> The figure inside started poking at the tarpaulin, prompting police to shoot at the boat.<ref name="AutoG4-1" />

According to Boston Police Commissioner Ed Davis and Watertown Police Chief Deveau, Dzhokhar Tsarnaev was shooting at police from inside the boat, "exchanging fire for an hour".<ref name="USA Today">{{cite news |url=https://www.usatoday.com/story/news/nation/2013/04/19/suspect-in-custody-newspaper-says/2095845/ |access-date=April 20, 2013 |title=As manhunt ends, new questions emerge in Boston bombings |author=Johnson, Kevin |work=USA Today |date=April 20, 2013}}</ref> A subsequent report indicated that the firing lasted for a shorter time.<ref name="auto">{{cite web|url=https://www.washingtonpost.com/world/national-security/officials-boston-suspect-had-no-firearm-when-barrage-of-bullets-hit-hiding-place/2013/04/24/376fc8a0-ad18-11e2-a8b9-2a63d75b5459_story.html|title=Officials: Boston suspect had no firearm when barrage of bullets hit hiding place|first1=Sari|last1=Horwitz|first2=Peter|last2=Finn|date=April 24, 2013|access-date=October 15, 2017|via=www.WashingtonPost.com}}</ref> Despite this, Tsarnaev was found to have no weapon when he was captured.<ref name="AutoLC-87" />

Dzhokhar Tsarnaev was arrested at 8:42{{nbsp}}p.m.<ref name="autogenerated2" /><ref name="autogenerated1" /> and taken to [[Beth Israel Deaconess Medical Center]], where he was listed in [[Medical state#Serious|critical condition]]<ref name="AutoLC-88" /> with gunshot wounds to the head, neck, legs, and hand.<ref name="AutoLC-89" /> Initial reports that the neck wound represented a suicide attempt were contradicted by Tsarnaev's being found unarmed.<ref name="AutoG4-2" /> The situation was chaotic, according to a police source quoted by ''[[The Washington Post]]'', and the firing of weapons occurred during "the fog of war".<ref name="auto" /> A subsequent review by the Commonwealth of Massachusetts provided this more specific summary: "One officer fired his weapon without appropriate authority in response to perceived movement in the boat, and surrounding officers followed suit in a round of '[[contagious shooting|contagious fire]]', assuming they were being fired on by Tsarnaev. Weapons continued to be fired for several seconds until on scene supervisors ordered a ceasefire and regained control of the scene. The unauthorized shots created another dangerous [[crossfire]] situation".<ref>{{cite web |url=http://www.mass.gov/eopss/docs/mema/after-action-report-for-the-response-to-the-2013-boston-marathon-bombings.pdf |title=After Action Report for the Response to the 2013 Boston Marathon Bombings |date=December 2014 |website=Government of Massachusetts |publisher=Executive Office of Public Safety and Security |access-date=October 10, 2017 |quote=Improvement Area 4, Lack of Weapons Discipline, page 114}}</ref> The confusion was caused in part by a lack of clearly identified and coordinated law enforcement command of the thousands of officers from surrounding communities who self-deployed into the Watertown area during the events.<ref>{{cite web |url=http://www.mass.gov/eopss/docs/mema/after-action-report-for-the-response-to-the-2013-boston-marathon-bombings.pdf |title=After Action Report for the Response to the 2013 Boston Marathon Bombings |date=December 2014 |website=Government of Massachusetts |publisher=Executive Office of Public Safety and Security |access-date=February 20, 2020 |quote=Improvement Areas 4.1 and 4.8, pages 113 & 117}}</ref>

After Dzhokhar Tsarnaev was taken into custody, the FBI revealed that it had investigated Tamerlan Tsarnaev in 2011 after a foreign nation had expressed concern about his potential radicalization. That investigation had included an interview of Tamerlan Tsarnaev. At that time, the FBI found no evidence of terrorist involvement by Tamerlan Tsarnaev.<ref>{{cite web|url=https://archives.fbi.gov/archives/news/pressrel/press-releases/2011-request-for-information-on-tamerlan-tsarnaev-from-foreign-government |title=2011 Request for Information on Tamerlan Tsarnaev from Foreign Government |website=archives.fbi.gov|date=April 19, 2013}}</ref>

On April 24, investigators reported that they had reconstructed the bombs, and believed that they had been triggered by remote controls used for toy cars.<ref name="la-times-bombs-triggered" />