SAN DIEGO (AP) — An unarmed security guard was shot and killed while working outside a San Diego homeless shelter by an attacker who remained at large, police said Sunday.

The guard, whose name has not been released, was on the sidewalk outside a downtown shelter Saturday night when he was shot several times. He was taken to a hospital where he died.

Several people on the sidewalk ran away when they heard gunfire and couldn’t give investigators a description of the shooter or even say if the shots came from a vehicle, Lt. Martha Sainz told the San Diego Union-Tribune.

The head of the nonprofit that runs the shelter, Alpha Project, told KNSD-TV 128 people were in the shelter when the shooting happened.