BOSTON -- Jurors in the Boston Marathon trial on Wednesday saw the tattered pieces of the backpack that Dzhokhar Tsarnaev used to carry a bomb in the deadly 2013 attack and heard a frantic call made by a policeman who found a Massachusetts Institute of Technology officer mortally wounded in his cruiser days after the bombing.
FBI Special Agent Sarah De Lair held up pieces of the black and white backpack for the jury. De Lair said the pieces were found near the Forum restaurant, where Tsarnaev planted and detonated a bomb April 15, 2013.
Three people were killed and more than 260 injured when Tsarnaev and his older brother, Tamerlan, set off two pressure cooker bombs near the marathon finish line.
Photos show debris and abandoned items scattered on the sidewalk and street -- clothing, a stroller, plastic water bottles and matching cowboy boots a few feet apart.
Dzhokhar Tsarnaev's lawyers have admitted he participated in the bombing but say Tamerlan was the mastermind. Tamerlan, 26, died in a shootout with police four days after the bombing.
Dzhokhar Tsarnaev, now 21, faces the possibility of the death penalty if convicted.
Later Wednesday, prosecutors began presenting testimony on the fatal shooting of MIT police Officer Sean Collier three days after the bombing.
MIT Police Chief John DiFava testified Wednesday that his last words to Collier were "Be safe." He said he briefly spoke to Collier when he saw him in his cruiser about an hour before Collier's death.
Fellow officer David Sacco described receiving a call from a resident who heard loud noises and saw an MIT cruiser outside. After being unable to reach Collier, Sacco sent another officer to check on him.
The jury heard a recording of that officer yelling, "Officer down! Officer down!" when he discovered Collier shot multiple times.
Collier was shot hours after the FBI released photos of the Tsarnaevs as suspects in the bombing and asked for the public's help in finding them.
Prosecutors say the Tsarnaev brothers killed Collier during an unsuccessful attempt to steal his gun. Dzhokhar Tsarnaev's lawyer said during opening statements that it was Tamerlan Tsarnaev who shot Collier.
