These deadly blasts sent shockwaves through Boston as well as the whole country.
It came at the end of a race that thousands of runners aspire to conquer -- and more than a year after the attack the trial is set to begin.
The two bombs killed three, and wounded more than 260 people in 2013's Boston Marathon.
And on Monday, Jury selection for accused bomber -- Dzhokhar Tsarnaev -- believed to have detonated a pair of homemade bombs at the finish line.
The 21-year-old ethnic Chechen faces the death penalty if convicted in federal court. He has pleaded not guilty to all 30 charges against him.
His 26-year-old brother Tamerlan was also named a suspect, and died after a wild gunbattle with police - just days after the bombing.
Experts say it will be virtually impossible to find jurors unaware of the basic details of the bombing. But the judge will seek to find a panel of 12 out of 1,200 prospective jurors.
The trial is expected to last three to five
