Boston Marathon bombing

== Initial investigation ==
[[File:Barack Obama discussing the 2013 Boston Marathon explosions.jpg|thumb|April 16 meeting in the [[Oval Office]] of the [[White House]] in which officials briefed President [[Barack Obama]] on the investigation (L–R: Homeland Security Secretary [[Janet Napolitano]]; Dept. Nat. Security Advr. [[Antony Blinken]]; Nat. Security Avdr. to the VP [[Jake Sullivan]]; USAG [[Eric Holder]]; Asst. to the President [[Lisa Monaco]]; Chief of Staff [[Denis McDonough]]; and FBI Dir. [[Robert Mueller]]; Obama)]]

The Federal Bureau of Investigation led the investigation, assisted by the [[Bureau of Alcohol, Tobacco, Firearms and Explosives]], the [[Central Intelligence Agency]], the [[National Counterterrorism Center]], and the [[Drug Enforcement Administration]].<ref name="Hosenball" /> It was initially believed by some that [[North Korea]] was behind the attack.<ref>{{Cite web|url=http://www.businessinsider.com/north-korea-blamed-for-boston-bombings-2013-4?IR=T|title=North Korea Adamantly Denies Conspiracy Theory Linking It to Boston Bombing|website=[[Business Insider]]}}</ref><ref>{{Cite web|url=http://www.ibtimes.com/north-korea-denies-any-link-boston-marathon-bombs-says-it-still-may-strike-us-1211721|title=North Korea Denies Any Link to Boston Marathon Bombs, but Says It Still May Strike US|website=[[International Business Times]]|date=April 24, 2013}}</ref>

United States government officials stated that there had been no intelligence reports suggesting such an attack. Representative [[Peter T. King|Peter King]], a member of the [[United States House Permanent Select Committee on Intelligence|House Intelligence Committee]], said: "I received two top secret briefings last week on the current threat levels in the United States, and there was no evidence of this at all."<ref name="AutoLC-46" />

Evidence found near the blast sites included bits of metal, nails, ball bearings,<ref name="McLaughlin" /> black nylon pieces from a backpack,<ref name="AutoLC-131" /> remains of an electronic circuit board, and wiring.<ref name="McLaughlin" /><ref name="Lister" /> A [[pressure cooker]] lid was found on a nearby rooftop.<ref name="AutoLC-49" /> Both of the [[improvised explosive device]]s were [[pressure cooker bomb]]s manufactured by the bombers.<ref name="abc-pressure-cooker" /><ref name="AutoLC-50" /><ref name="AutoLC-51" /> Authorities confirmed that the brothers used bomb-making instructions found in [[Al Qaeda in the Arabian Peninsula]]'s ''[[Inspire (magazine)|Inspire]]'' magazine.<ref name="Auto9P-1" /><ref name="la-times-suspect-describes-plot" /> After the suspects were identified, ''[[The Boston Globe]]'' reported that Tamerlan purchased [[fireworks]] from a fireworks store in [[New Hampshire]].<ref name="AutoQU-2" />

{{multiple image
 | width = 200px
 | align = left
 | image1 = Tsarnaev Fireworks.jpg
 | caption1 = Emptied fireworks from Dzhokhar Tsarnaev's backpack, found in a landfill near the UMass Dartmouth campus
 | alt1 =
 | image2 = Pressure cooker bomb.jpg
 | caption2 = Recovered pressure cooker fragment from one of the explosive devices
 | alt2 =
 | image3 = Workers in hazardous material suits walk away from the scene of the bombing on Boylston Street (8673683434).jpg
 | caption3 = Workers in [[hazmat suit]]s inspecting the finish line area on April 20
 | alt3 =
}}
{{Clear}}