Boston Marathon Bombing

On April 15, 2013, during the 117th Boston Marathon, two homemade pressure cooker bombs detonated 14 seconds and 210 yards apart near the finish line on Boylston Street in Boston, Massachusetts. The explosions killed three civilians — Krystle Marie Campbell, 29; Lu Lingzi, 23; and 8-year-old Martin William Richard — and injured 264 others, including 16 people who lost limbs. Rescue and medical personnel already stationed for the marathon provided immediate aid, and authorities closed a large area around the blast site as investigators searched for explanations, initially suspecting no known threat had been flagged by intelligence agencies.

The FBI led the investigation, working with the ATF, CIA, National Counterterrorism Center, and DEA. Evidence recovered at the scene — including ball bearings, nails, and pressure cooker fragments — indicated the devices were homemade. On April 18, three days after the bombing, the FBI released images of two unidentified suspects, later identified as brothers Tamerlan and Dzhokhar Tsarnaev.

That evening, the brothers shot and killed MIT Police officer Sean Collier, 27, in his patrol car, then carjacked a vehicle in Allston-Brighton, taking the owner hostage before he escaped. Officers located the brothers in Watertown, where a shootout ensued in which an estimated 200-300 shots were fired and the brothers threw improvised explosives. Tamerlan Tsarnaev was shot and then run over by his brother as he fled in the stolen vehicle; Tamerlan died shortly afterward at a hospital. Boston Police officer Dennis Simmonds was injured by a grenade during the shootout and died from his injuries on April 10, 2014. MBTA officer Richard Donohue Jr. was critically wounded by crossfire but survived.

An extensive manhunt followed, with a 20-block area of Watertown searched door-to-door and residents of surrounding communities asked to shelter in place. On the evening of April 19, a Watertown resident discovered Dzhokhar Tsarnaev hiding in a boat in his backyard. Tsarnaev was shot and wounded by police before being taken into custody.

During questioning, Dzhokhar Tsarnaev acknowledged his role in the bombings, stating that he and his brother were motivated by U.S. military action in Iraq and Afghanistan, were self-radicalized, and had learned bomb-making from Inspire magazine, published by al-Qaeda in the Arabian Peninsula. He said the brothers had also intended to bomb Times Square in New York City.

Tsarnaev was charged in federal court with use of a weapon of mass destruction and other offenses. His trial began in March 2015, and on April 8, 2015, he was convicted on all 30 counts. He was sentenced to death on June 24, 2015. In July 2020, an appeals court vacated the death sentence over jury-selection issues, but on March 4, 2022, the U.S. Supreme Court reversed that ruling and reinstated the death sentence. Several associates of Dzhokhar Tsarnaev, including roommates and an acquaintance of Tamerlan, were separately charged and convicted of obstruction-related offenses for actions taken after the bombing.