2013 Boston Marathon Bombing

On Patriots' Day, April 15, 2013, two homemade pressure-cooker bombs were detonated near the finish line of the Boston Marathon, striking one of the city's most beloved annual traditions and sending shockwaves across the nation. As runners from around the world were cheered by thousands of spectators lining Boylston Street for the 117th Boston Marathon, two self-radicalized brothers, Tamerlan and Dzhokhar Tsarnaev, detonated two improvised explosive devices near the finish line, killing three people and injuring more than 260 others in the immediate blast area, with more than 500 people sustaining physical injuries in total. The attack, which unfolded in the city's Back Bay neighborhood, triggered a multi-day manhunt that brought Greater Boston to a standstill and resulted in one of the most intensive law-enforcement operations in American history.

Background and Setting

April 15, 2013, marked the 117th running of the Boston Marathon, the world's oldest annual marathon. The popular event is held on Patriots' Day, a Massachusetts state holiday that commemorates the 1775 Battles of Lexington and Concord that began the American Revolutionary War. The festive atmosphere draws hundreds of thousands of spectators to the 26.2-mile (42.195 km) route from Hopkinton, Massachusetts, to Boston's Back Bay neighborhood. In 2013, there were 26,893 official entrants, and more than 500,000 people gathered along the marathon route to cheer on runners and celebrate the holiday.

The race's finish line on Boylston Street, flanked by tens of thousands of spectators, was the most densely crowded section of the course when the bombs were detonated that afternoon. Security arrangements for the 2013 race followed standard protocols for large public events, including a significant presence from the Boston Police Department, the Massachusetts State Police, and the Boston Athletic Association's own staff — protocols that would be substantially revised in the wake of the attack.

The Bombing

At 2:49 p.m., the first of two bombs was detonated at 671 Boylston Street; the second bomb was detonated thirteen seconds later, approximately 180 yards farther up the course at 755 Boylston Street. It was later determined that the explosions were caused by homemade improvised explosive devices (IEDs) hidden in backpacks and placed on the ground level in crowded viewing areas just seconds before they were detonated.

The devices used in the attacks were household pressure cookers packed with an explosive substance, nails, and ball bearings — the nails and ball bearings serving as shrapnel when the bombs detonated, which accounts for the severity of injuries among those nearest to the blasts.

The bombs killed three people: Martin Richard, age 8; Krystle Campbell, age 29; and Lu Lingzi, age 23. More than 260 people were injured in the immediate blast, and more than 500 people were physically injured in total, including 17 who suffered amputations. According to data from the One Fund Boston, 281 people were treated at 26 hospitals across the region. Within one and a half hours of the initial explosions, 78 percent of the patients treated at trauma centers had already arrived, a testament to the speed of the emergency response.

The immediate aftermath on Boylston Street was chaotic. Following the explosions, emergency responders — police, fire, and EMS — along with Boston Athletic Association medical volunteers from the Alpha Medical Tent and numerous spectators and bystanders quickly moved to aid the critically injured, triaging wounds and facilitating transport to area hospitals. The presence of medical personnel already stationed at the finish line to treat runners proved critical in the minutes immediately following the blasts, and is widely credited with preventing an even higher death toll.

Victims

Three people were killed in the bombings. Martin Richard, an 8-year-old boy from the Dorchester neighborhood of Boston, had gone to the finish line with his family to watch a family friend cross. He was the youngest victim. Krystle Campbell, 29, was a restaurant manager from Medford, Massachusetts, who had come to the finish line to watch a friend run the race. Lu Lingzi, 23, was a Chinese graduate student at Boston University who was at the finish line with friends. All three were killed by the force of the blasts and the shrapnel contained in the devices.

Massachusetts Institute of Technology Police Officer Sean Collier, age 27, was also killed in connection with the attack. On the night of April 18, 2013, the Tsarnaev brothers ambushed Collier as he sat in his patrol car near Building 32 on the MIT campus, shooting him six times. The brothers were attempting to steal his service weapon but were unable to free it from its security retention holster. Collier died shortly thereafter. He is remembered as a victim of the broader attack and is memorialized alongside the three marathon bombing victims in tributes around the Boston area.

BPD Sergeant Dennis "DJ" Simmonds, age 28, of Randolph, Massachusetts, died on April 10, 2014, as a result of a severe head injury sustained during the Watertown confrontation on April 19, 2013, when the Tsarnaev brothers hurled explosive devices at officers. He is also recognized as a victim of the attack, and his sacrifice has been commemorated through multiple memorial dedications across the region.

The Perpetrators

The brothers responsible for the attack, Tamerlan Tsarnaev and Dzhokhar Tsarnaev, were born in the former Soviet republic of Kyrgyzstan — Tamerlan in 1986 and Dzhokhar in 1993 — and had immigrated to the United States as children with their family, eventually settling in Cambridge, Massachusetts. Both brothers were Muslim, and investigators concluded that they had become self-radicalized through online extremist content in the years prior to the attack. Dzhokhar Tsarnaev later cited the Islamic State as an inspiration, and both brothers expressed grievances over United States military involvement in Muslim-majority countries.

At the time of the bombings, Dzhokhar Tsarnaev was a 19-year-old sophomore at the University of Massachusetts Dartmouth. Tamerlan Tsarnaev, 26, was a former amateur boxer who was married and had a young child. Investigators concluded that the brothers planned and carried out the attack on their own and were not formally connected to any foreign terrorist organization, though their radicalization was heavily influenced by extremist materials available online.

Prior to the bombing, Russian officials had contacted the FBI requesting a review of Tamerlan Tsarnaev's possible ties to extremists. The FBI conducted an assessment but found no actionable evidence at the time, and local law enforcement in Boston was not informed of the inquiry. This gap in information sharing became a significant point of scrutiny in the post-attack investigation and prompted changes in inter-agency communication protocols.

The Manhunt

On April 18, 2013, three days after the bombing, the FBI released images and video of two men identified as suspects, including a photograph showing one of the men placing a backpack at the location of the second explosion. The suspects were quickly identified as the Tsarnaev brothers. That same evening, at approximately 10:25 p.m., the brothers ambushed and fatally shot MIT Police Officer Sean Collier as he sat in his patrol car near Building 32 on the MIT campus, in what investigators believe was an attempt to obtain a firearm.

Following the Collier shooting, the brothers carjacked a vehicle and kidnapped its driver, forcing him to drive to a gas station while robbing him of $800. The driver managed to escape, and the brothers then drove to Watertown, Massachusetts. Shortly after midnight on April 19, police spotted the suspects and attempted to apprehend them. A prolonged gun battle erupted on Laurel Street in Watertown, during which the Tsarnaevs exchanged fire with officers and hurled multiple improvised explosive devices at them. Tamerlan Tsarnaev was fatally wounded during the firefight and later pronounced dead at a hospital. Dzhokhar Tsarnaev fled the scene in the carjacked vehicle, running over his brother in the process, and escaped into the surrounding neighborhood.

On the morning of April 19, Massachusetts Governor Deval Patrick and other officials issued an unprecedented shelter-in-place request for Boston and surrounding communities, asking residents to remain indoors and businesses to stay closed as an intensive manhunt for Dzhokhar Tsarnaev unfolded across the region. Much of Greater Boston came to a standstill, with public transit suspended and streets largely empty. The "stay home" order was lifted at 6:00 p.m. that evening, after a Watertown resident went to his backyard to check on a boat parked there, noticed that its protective tarp had come loose, and, while adjusting it, discovered Dzhokhar Tsarnaev hiding inside. Police soon arrived, and after a brief standoff during which shots were exchanged and Tsarnaev was wounded, he was taken into custody.

Investigation

The investigation that followed the bombing was one of the largest law-enforcement undertakings in the city's history. FBI Boston's Evidence Response Team (ERT), working with teams from the Boston Police Department, the Massachusetts State Police, and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), spent nine days processing 12 square blocks near the bomb scenes. Approximately 176 FBI Laboratory and ERT personnel were deployed to Boston, and evidence technicians processed more than 3,500 pieces of evidence, shipping 2,749 items to the FBI Laboratory in Quantico, Virginia, for further analysis.

More than 33 terabytes of digital information were collected, including photos and video submitted by the public through a special digital tip line developed to support the investigation. Linguists spent more than 2,500 hours translating material to support both the investigation and the subsequent trial. Ultimately, more than 20 law enforcement agencies with more than 1,000 investigators joined the effort, according to a Boston Globe account.

The investigation also scrutinized prior intelligence. Before the bombing, Russian officials had asked the FBI to look into Tamerlan Tsarnaev's possible ties to extremists, but police in Boston were not informed. The handling of that tip became a central point of discussion in post-attack reviews and contributed to changes in how federal and local agencies share counterterrorism intelligence.

Trial, Sentencing, and Legal Aftermath

In July 2013, Dzhokhar Tsarnaev pleaded not guilty to 30 federal charges against him, including the use of a weapon of mass destruction resulting in death. On April 8, 2015, a federal jury found him guilty on all 30 counts, and he was subsequently sentenced to death by lethal injection. At his sentencing hearing, Tsarnaev addressed survivors and the families of victims, offering an apology for the attack.<ref>{{cite web |title=Boston Marathon Bombing — Victims, Suspects & Facts |url=https://www.history.