Richmond police in California's Bay Area are trying to piece together the mystery of how a former NFL player lost his life on Wednesday. Terrell Roberts, a 38-year-old athlete who played for the Cincinnati Bengals from 2003 to 2005, was reportedly visiting his grandmother's home when he was shot and killed in her backyard.

According to KPIX 5 News, an unknown assailant made his way into the grandmother's residence and opened fired on Roberts before fleeing the scene. Witnesses told investigators that they heard a "disturbance" and saw Roberts falling over. Responding police officers found Roberts dead at the scene with a single bullet wound to his chest. It's suspected that the shooter—who is described as a bald black male with a short beard between 20 and 35-years-old weighing about 250 pounds—and Roberts first argued in the garage before the former Bengals player was shot in the yard.

A neighbor told the news station that he spoke with Roberts's grandmother who couldn't believe that anyone who would harm him. "She was saying that she knew some of his so-called friends but she doesn’t know who it was, why they would do it to him," he said. "She didn’t know."