Rockville, Md. ? Convicted sniper John Allen Muhammad, representing himself in his second trial stemming from the October 2002 Washington-area shootings, questioned witnesses Friday on the point that no one actually saw the gunman.

Prosecutors began their case by asking witnesses to describe the sound of a gunshot and the collapse of the sniper’s first victim.

Kimberly Sadelson, who had been grocery shopping in Wheaton, described hearing “a loud bang” and turning to see James Martin fall down. She said she called 911 and saw Martin lying on the ground.

“He wasn’t moving,” she said.

Muhammad asked Sadelson whether she had seen who had fired the shot and asked whether she had seen Martin before he was shot. She answered “no” to both questions.

Muhammad is on trial for six murders in Montgomery County, where the shooting spree that killed 10 people and wounded three began and ended. He has been sentenced to death for a Virginia killing.