The Boston Marathon bombing, sometimes referred to as simply the Boston bombing, was an Islamist domestic terrorist attack that took place during the 117th annual Boston Marathon on April 15, 2013. Four hours into the race, Tamerlan Tsarnaev and Dzhokhar Tsarnaev detonated two homemade pressure cooker bombs containing explosives and steel shrapnel. The bombs were hidden inside two backpacks dropped in the cheering crowds just minutes prior, and remotely detonated near the finish line of the race in central Boston, 14 seconds and 210 yards (190 m) apart. Three people were killed and hundreds were injured, including 12 victims who suffered traumatic limb amputations.
On April 18, 2013, the Federal Bureau of Investigation (FBI) released images of two suspects in the bombing. The two suspects were later identified as the Tsarnaev brothers. Late on the evening of April 18, the brothers killed an MIT policeman, Sean Collier, in a failed attempt to steal Collier's service pistol, and proceeded to commit a carjacking close by. They engaged in a shootout with police in nearby Watertown, during which two officers were severely injured (one of the officers, Dennis Simmonds, died a year later from his injuries). Dzhokhar was struck in the face by a bullet, and Tamerlan was shot in the limbs and torso several times, followed by Dzhokhar striking him at high speed by the stolen car while attempting to run over police officers. Tamerlan was dragged down the road while stuck under the car, and died in a hospital soon after.
An unprecedented search for Dzhokhar Tsarnaev ensued, with thousands of law enforcement officers in tactical gear searching door-to-door in a roughly 20-block area of Watertown. Residents of Watertown and surrounding communities were asked to stay indoors. The public transportation systems, along with local businesses and public places, were closed or shut down. After a brief manhunt, a Watertown resident called 911 and alerted the police of the possible presence of Dzhokhar, who had climbed and hidden inside a boat under a white tarp, in his backyard. He was shot at and suffered multiple additional gunshot wounds during a several hours long standoff, which involved the use of armored vehicles, before surrendering. The police then took him into custody on the evening of April 19.
During questioning, Dzhokhar Tsarnaev acknowledged his role in the bombings. He said that he and his brother were motivated by the wars in Iraq and Afghanistan, that they were self-radicalized and unconnected to any outside terrorist groups, and that he was merely following his brother's lead. He said the brothers learned to build explosive devices from Inspire, the online magazine of al-Qaeda in the Arabian Peninsula. He also said that they had intended to travel to New York City to bomb Times Square. In April 2015, Dzhokhar Tsarnaev was convicted of all 30 charges in federal court, including the use of a weapon of mass destruction and malicious destruction of property resulting in death. Two months later, he was sentenced to the death penalty. The sentence was upheld on appeal by the Supreme Court of the United States on March 4, 2022. Dzhokhar has remained on death row ever since, and is currently incarcerated in the United States' maximum security prison, ADX Florence.
Bombing
The 117th annual Boston Marathon was run on Patriots' Day, April 15, 2013. At 2:49 p.m. EDT (18:49 UTC), two bombs detonated about 210 yards (190 m) apart at the finish line on Boylston Street near Copley Square. The first exploded outside Marathon Sports at 671–673 Boylston Street at 2:49:43 p.m. At the time of the first explosion, the race clock at the finish line showed 04:09:43—the elapsed time since the Wave 3 start at 10:40 a.m. The second bomb exploded at 2:49:57 p.m., 14 seconds later and one block farther west at 755 Boylston Street. The explosions took place nearly two hours after the winning runner crossed the finish line, but with more than 5,700 runners yet to finish.
Windows on adjacent buildings were blown out, but there was no structural damage. Runners continued to cross the line until 2:57 p.m.
Casualties and initial response
Rescue workers and medical personnel, on site as usual for the marathon, gave aid as additional police, fire, and medical units were dispatched, including from surrounding cities as well as private ambulances from all over the state. The explosions killed three civilians and injured 264 others.
Police, following emergency plans, diverted all remaining runners to Boston Common and Kenmore Square. The nearby Lenox Hotel and other buildings surrounding the scene were evacuated. Immediately after the bombing occurred and medically injured people were transported, the police closed a 15-block area around the blast site; this was reduced to a 12-block crime scene the next day. Boston police commissioner Edward F. Davis recommended that people stay off the streets.
Dropped bags and packages, abandoned as their owners fled from the blasts, increased uncertainty as to the possible presence of more bombs and many false reports were received. Simultaneously an electrical fire at the John F. Kennedy Presidential Library in nearby Dorchester was initially feared to be a bomb.
The airspace over Boston was restricted, and departures halted from Boston's Logan International Airport. Some local transit service was halted as well.
The Massachusetts Emergency Management Agency suggested that people trying to contact those in the vicinity use text messaging instead of voice calls because of the crowded cell phone lines. Cell phone service in Boston was congested but remained in operation, despite some media reports stating that cell service was shut down to prevent cell phones from being used as detonators.
The American Red Cross helped concerned friends and family receive information about runners and casualties. The Boston Police Department also set up a call helpline for people concerned about relatives or acquaintances to contact and a line for people to provide information. Google Person Finder activated their disaster service under Boston Marathon Explosions to log known information about missing people as a publicly viewable file.
Due to the closure of several hotels near the blast zone, a number of visitors were left with nowhere to stay; many Boston-area residents opened their homes to them.
Initial investigation
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. It was initially believed by some that North Korea was behind the attack.
United States government officials stated that no intelligence reports suggested such an attack. Representative Peter King, a member of the 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."
Evidence found near the blast sites included bits of metal, nails, ball bearings, black nylon pieces from a backpack, remains of an electronic circuit board and wiring. A pressure cooker lid was found on a nearby rooftop. Both of the improvised explosive devices were pressure cooker bombs manufactured by the bombers. Authorities confirmed that the brothers used bomb-making instructions found in al-Qaeda in the Arabian Peninsula's Inspire magazine. After the suspects were identified, The Boston Globe reported that Tamerlan purchased fireworks from a fireworks store in New Hampshire.
April 18–19 shootings and search
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". He later gave a detailed description of the suspects, which enabled images of them to be identified and circulated quickly.
At 5:00 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. The FBI said that they were doing this in part to limit harm to people wrongly identified by news reports and on social media.
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. The FBI-released images depicted Dzhokhar and Tamerlan Tsarnaev.
MIT shooting and carjacking
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.
On April 18, 2013 at 10:25 p.m., the Tsarnaev brothers ambushed and shot Sean A. Collier of the Massachusetts Institute of Technology Police Department six times. The two brothers were attempting to steal Collier's Smith & Wesson M&P45 sidearm, which they could not free from his holster because of its security retention system. Collier, aged 27, was seated in his police car near Building 32 on the Massachusetts Institute of Technology campus. He died shortly after the shooting.
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 (Chinese: 孟盾), hostage and told him that he was responsible for the Boston bombing and for shooting Collier. 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.
The Tsarnaev brothers forced Meng to give up his bank card and PIN number to obtain $800 in cash (equivalent to $1,106 in 2025) from an ATM. They transferred objects to the Mercedes-Benz and one brother followed it in their Civic, for which an all-points bulletin was issued. The brothers then drove to a Shell gas station on Memorial Drive in Cambridge to fill up for the long drive (208 miles) to Times Square. While Tamerlan pumped gas and Dzhokhar went inside the Shell station to pay for food, Meng, fearing that his assailants would likely harm or kill him during the drive, escaped from the Mercedes and sprinted across the street to a Mobil gas station, frantically pleading with the clerk to call 911. Meng's Mercedes had a GPS system that allowed the car’s location to be tracked in real time, so Meng provided the tracking number to the police to help them find the Tsarnaev brothers' exact location.
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.
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. 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.
According to Watertown Police Chief Edward Deveau, the brothers had an "arsenal of guns". Tamerlan eventually ran out of ammunition and threw his empty Ruger pistol at Watertown PD Sergeant Jeffrey Pugliese, who then tackled him with assistance from Sergeant MacLellan.
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; 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. Dzhokhar abandoned the car half a mile away and fled on foot. Badly wounded, Tamerlan Tsarnaev was taken into custody and died at 1:35 a.m. at Beth Israel Deaconess Medical Center.
Massachusetts Bay Transportation Authority Police Officer Richard H. Donohue Jr. was critically wounded in the leg 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. Boston Police Department officer Dennis Simmonds was injured by a hand grenade and died on April 10, 2014. Fifteen other officers were also injured. 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.
Only one firearm, Tsarnaev's Ruger P95, was recovered at the scene. That firearm was found to have a defaced serial number.
Further investigation and post-shootout search for Dzhokhar Tsarnaev
Records on the Honda left at the Watertown shootout scene identified the bombers Tamerlan and Dzhokhar "Jahar" Tsarnaev. The FBI released additional photos of the two during the Watertown incident. Early on April 19, investigators released the name and photo of Dzhokhar Tsarnaev to the public. In addition, Watertown residents received automated calls asking them to stay indoors. That same morning Governor Patrick asked residents of Watertown and adjacent cities and towns to "shelter in place". Somerville residents also received automated calls instructing them to shelter in place.
A 20-block area of Watertown was 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. 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 circumstances. Agencies on the scene were the FBI; the Bureau of Alcohol, Tobacco, Firearms, and Explosives; Diplomatic Security Service; HSI-ICE; 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.