HOUSTON (AP) — The U.S. Justice Department is investigating six cases over the last two years in which Houston police officers fatally shot or allegedly used excessive force against unarmed individuals, police officials said Wednesday.

One case involves the September shooting death of Brian Claunch, 45, a mentally ill one-armed, one-legged man in a wheelchair. Officers responding to a disturbance at the group home where Claunch lived said he threatened them with what turned out to be a ballpoint pen.