Boston Marathon bombing timeline

A timeline follows of events related to the Boston Marathon bombing, which killed three people and injured more than 260 others on April 15, 2013. On May 15, 2015,, a federal jury sentenced convicted bomber Dzhokhar Tsarnaev to die by lethal injection.

March 2011

Russian FSB intelligence security service gives FBI information that Tamerlan Tsarnaev, of Cambridge, Mass., is a follower of radical Islam.

June 2011

FBI closes investigation after finding nothing to link Tamerlan Tsarnaev to terrorism.

Sept. 12, 2011

Bodies of three men are found in Waltham, Mass., with their throats slit and marijuana sprinkled over them.

Late 2011

U.S. officials add the Tsarnaevs' mother to a federal terrorism database after Russia contacts CIA with concerns they were religious militants about to travel to Russia. She later says she has no links to terrorism.

January 2012

Tamerlan arrives in Russia, where he spends time in two predominantly Muslim provinces, Dagestan and Chechnya.

July 2012

Officials in Dagestan say Tamerlan applies for a new passport but never picks it up. Russian officials say they have him under surveillance but lose track of him after the death of a Canadian man who had joined an Islamic insurgency in the region.

July 17, 2012

Tamerlan returns to U.S.

November 2012

Islamic Society of Boston Cultural Center in Cambridge says Tamerlan has an outburst that interrupts a sermon about it being acceptable for Muslims to celebrate American holidays.

January 2013

Islamic Society says Tamerlan has a second outburst after a sermon that includes praise for the Rev. Martin Luther King Jr.

April 15, 2013

Bombs go off at the finish line of the Boston Marathon, killing three people and injuring more than 260 others.

April 16, 2013

Federal agents say the bombs were made from pressure cookers packed with explosives, nails and other shrapnel, but they still don't know who detonated them or why.

April 17, 2013

U.S. President Barack Obama signs emergency declaration for Massachusetts and orders federal aid to supplement local response.

April 18, 2013

Investigators release photos and video of two suspects and ask for public's help identifying them. Later that night, Massachusetts Institute of Technology police officer Sean Collier is shot to death in his cruiser, allegedly by Tamerlan and Dzhokhar Tsarnaev. Prosecutors say they steal an SUV at gunpoint from a Cambridge gas station. The driver is held for about a halfhour, then released unharmed.

April 19, 2013

Tsarnaevs have an early morning gun battle with authorities who have tracked them to Watertown. Tamerlan, who is run over by his younger brother, dies. Dzhokhar escapes, and around 6 a.m., authorities tell residents of Boston and surrounding communities to stay indoors. All mass transit is shut down. That order is lifted around 6:30 p.m., just before authorities trace Dzhokhar to a Watertown backyard, where he is found hiding in a boat and taken into custody.

April 22, 2013

Dzhokhar Tsarnaev, injured in the shootout, is charged in his hospital room with using and conspiring to use a weapon of mass destruction.

April 30, 2013

Two friends of Dzhokhar's are charged with attempting to destroy evidence by disposing of a backpack and laptop computer taken from his room after they found he was a suspect in the bombing. Another is charged with lying to investigators.

May 9, 2013

Tamerlan Tsarnaev is secretly buried in Virginia after a weeklong search for a cemetery willing to take the body.

May 22, 2013

An FBI agent in Orlando, Fla., fatally shoots Ibragim Todashev, a friend of Tamerlan's, after he lunges at law enforcement officials questioning him about the Waltham killings. Officials say that before he died, he had agreed to give a statement about his involvement.

July 10, 2013

Dzhokhar Tsarnaev pleads not guilty to 30 federal charges.

July 23, 2013

Marc Fucarile is the last survivor of the bombings to leave the hospital.

Jan. 30, 2014

Prosecutors announce they will seek the death penalty against Dzhokhar.

April 15, 2014

Ceremonies and events mark the anniversary of the attacks.

April 21, 2014

The 2014 Boston Marathon features a field of 36,000 runners, 9,000 more than 2013 and the second-biggest field in history.

May 30, 2014

Khairullozhon Matanov, 23, is arrested on charges of obstructing the investigation by deleting information from his computer and lying to investigators.

June 18, 2014

Tsarnaev's lawyers file first of several requests to move the trial to Washington, D.C.

July 21, 2014

Azamat Tazhayakov, a college friend of Dzhokhar's, is convicted of obstruction of justice and conspiracy for agreeing with another friend to get rid of a backpack and disabled fireworks they took from his dorm room three days after the attack.

July 22, 2014

Stephen Silva, believed to have provided the gun used by the Tsarnaevs to kill Collier, is arrested on drug and weapons charges.

Aug. 22, 2014

Dias Kadyrbayev, 20, pleads guilty to impeding the investigation by removing incriminating evidence from Dzhokhar's dorm room.

Sept. 24, 2014

Judge grants delay and pushes start of trial to Jan. 5, 2015.

Oct. 28, 2014

Robel Phillipos, 21, is convicted of lying to federal agents about being in Dzhokhar's room.

Nov. 25, 2014

Federal judge rejects a request from lawyers for Tsarnaev to order prosecutors to turn over evidence about his older brother's possible participation in the Waltham slayings.

Dec. 18, 2014

Tsarnaev appears in court for first time since his July 2013 arraignment.

Jan. 5, 2015

Jury selection begins in Tsarnaev's trial.

March 4, 2015

Tsarnaev's lead defence attorney, Judy Clarke, declares in opening statements: "It was him."

April 6, 2015

Prosecutors and defence present closing statements.

April 7, 2015

Jury begins deliberating verdicts.

April 8, 2015

Jury convicts Tsarnaev; will weigh possible death sentence in forthcoming penalty phase of trial.

April 15, 2015

Second anniversary of Boston Marathon bombings.

April 20, 2015

119th running of the Boston Marathon.

April 21, 2015

Penalty phase of Tsarnaev's trial begins.

May 13, 2015

Prosecutors and defence make closing statements on sentence; jury begins deliberating.

May 15, 2015

Exactly 25 months after the attack, jury sentences Tsarnaev to death.