The Boston Marathon bombing was a terrorist attack, followed by subsequent related shootings, that occurred when two pressure cooker bombs exploded during the Boston Marathon on April 15, 2013. The bombs exploded about 12 seconds and 210 yards (190 m) apart at 2:49 pm EDT, near the marathon's finish line on Boylston Street. They killed 3 civilians and injured an estimated 264 others.
The Federal Bureau of Investigation (FBI) took over the investigation and, on April 18, released photographs and a surveillance video of two suspects. The suspects were identified later that day as Chechen brothers Dzhokhar Tsarnaev and Tamerlan Tsarnaev. Shortly after the FBI released identifying images publicly, the suspects killed an MIT policeman, carjacked a civilian SUV, and initiated an exchange of gunfire with the police in Watertown, Massachusetts. During the firefight, an MBTA police officer was injured but survived with severe blood loss. Tamerlan Tsarnaev was shot several times in the firefight and his brother subsequently ran him over with the stolen SUV in his escape. Tamerlan was pronounced dead at the scene.
An unprecedented manhunt for Dzhokhar Tsarnaev ensued on April 19, with thousands of law enforcement officers searching a 20-block area of Watertown. During the manhunt, authorities asked residents of Watertown and surrounding areas, including Boston, to stay indoors. The public transportation system and most businesses and public institutions were shut down, creating a deserted urban environment of historic size and duration. Around 6:00 p.m., shortly after the "shelter-in-place" advisory was rescinded, a Watertown resident discovered Dzhokhar hiding in a boat in his back yard. Reports conflict as to whether or not he was armed. Located within the boat by thermal imaging, he was shot while in the boat, arrested, and then taken to a hospital shortly thereafter.
During an initial interrogation in the hospital, Dzhokhar alleged that Tamerlan was the mastermind. He said they were motivated by extremist Islamist beliefs and the wars in Iraq and Afghanistan, and that they were self-radicalized and unconnected to any outside terrorist groups. According to him, they learned to build explosive devices from an online magazine of the al-Qaeda affiliate in Yemen. He said that he and his brother had decided after the Boston bombing to travel to New York City to bomb Times Square. Dzhokhar was indicted on April 22, while still in the hospital, on 30 charges relating to homegrown terrorism, including use of a weapon of mass destruction and malicious destruction of property resulting in death. He was found guilty on all charges on April 8, 2015, and the following month was sentenced to death.