Kwaku Agyin, 21, is facing a slew of charges, related to an Oct. 2, 2011, shooting in which prosecutors say he killed Marcus Anderson, 29, after Anderson tried to steal away his prostitute.
That teen took the stand on Thursday and told the court she began prostituting for Agyin after moving from Houston, and meeting him at a bus stop in San Antonio.
It was sometime later that she met Anderson and began dealing drugs for him.
All of this lead to a confrontation at the Skyline Motel between the two men last October, prosecutors said.
The teen girl testified today that she witnessed Agyin shoot Anderson.
"I had tried to reach for the gun to get ahold of it, and pass it to Marcus,” said the teen. “I was trying to push it toward him because Marcus was on the ground. Kwaku had come back, pushed the gun away and still was shooting.”
If convicted, Agyin is facing a maximum of 12 life sentences on sex and child trafficking charges.
He faces another life sentence on the murder charge.