WARNING: This report contains graphic images that may be disturbing.
Dzhokhar Tsarnaev showed no reaction to the vivid and powerful stories delivered just feet in front of him, but jurors and spectators in the courtroom found it painful to hear.
In many cases, they were brought to tears, reports CBS News correspondent Elaine Quijano.
Of the survivors and first responders who testified Thursday, Bill Richard may have been the most heartbreaking. His 6-year-old daughter Jane lost her leg, his 8-year-old son Martin was killed.
In images shown publicly for the first time in court, the backpack dropped by Tsarnaev is seen right behind the family.
Richard revisited the moments after the explosions.
"I saw a little boy who had his body severely damaged by an explosion. And I knew from what I saw there was no chance."
He then walked to his daughter Jane and "noticed her leg, she didn't have it."
One of the lasting photos of the tragedy is of Jeff Bauman, who lost both of his legs in the bombing. He recalled seeing Tamerlan Tsarnaev.
"I looked at him... he wasn't having fun." Then Bauman noticed a bag on the street and told his friend, "maybe we should get out of here."
Seconds later, he was knocked to the ground. Bauman looked at his legs and could see flesh and bone. "This is how it's going to end," he recalled telling himself.
For Rebekah Gregory, testifying provided a form of relief. She lay on the pavement in agony after the second bomb exploded, leaving her with a devastating injury to her left leg.
"Right before I walked in, I was dreading it," Gregory said.
The 27-year-old posted an open letter to Tsarnaev on Facebook. "I have been truly scared of you and because of this, fearful of everything else people might be capable of," she wrote.
"When I walked into the courtroom and I was able to look him in the face, I realized that that fear was gone. And I wasn't afraid. And he became a nobody to me again," Gregory said.
Seventeen prosecution witnesses have so far delivered testimony. The trial resumes Monday.