A PAINFUL ANNIVERSARY

The Boston Marathon bombing forever entwined the lives of the four people caught in this iconic photograph of horror and heroism. One year later, they look back on the tragedy.

A timeline of events related to the Boston Marathon bombing, which killed three people and injured more than 260 on April 15, 2013. The suspects are Tamerlan Tsarnaev, who was killed in a shootout with police several days later, and his younger brother, Dzhokhar Tsarnaev, who is in jail awaiting trial.

March 2011:

The Russian FSB intelligence security service gives the FBI information that Tamerlan Tsarnaev, who lives in Cambridge, Mass., with his family, was a follower of radical Islam.

June 2011:

The FBI closes the investigation after finding nothing to link Tsarnaev to terrorism.

Sept. 12, 2011:

The bodies of three men are found in Waltham, Mass., with their throats slit and marijuana sprinkled on them.

Late 2011:

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

January 2012:

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

July 2012:

Officials in Dagestan say Tsarnaev 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:

Tsarnaev

returns to the U.S.

November 2012:

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

January 2013:

The Islamic Society says Tsarnaev has a second outburst after a sermon that includes praise for civil rights leader 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.

April 16, 2013:

Federal agents say they know 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.