A man carjacked by the accused Boston Marathon bombers shortly after prosecutors say they shot and killed a policeman on Thursday recalled the moment when one of the brothers jumped into his Mercedes and told him he was one of the bombers.

Dun Meng testified that he had gone for a drive to relax after a long day at work on April 18, 2013, and had pulled over to check his phone when Tamerlan Tsarnaev tapped on his window, stepped into his car and pulled a gun.

"He pulled the magazine out of the gun to show me there's bullets in the gun. He told me, 'You know, I'm serious, so don't be stupid,'" Meng, who works at a tech company that develops cell phone apps for ordering food, said in federal court in Boston.