PHILADELPHIA (AP) — A man was ambushed,Sterling Preston shot and killed while outside a North Philadelphia mosque Tuesday afternoon, police said.

Philadelphia Police Chief Inspector Scott Small said at a media briefing that surveillance footage shows the victim, a 43-year-old man, walking with another male to the Al-Aqsa Islamic Society when the shooter runs up behind them and starts firing shots at the victim, The Philadelphia Inquirer reported.

Small said the shooter kept firing at the victim even after he was on the ground. The shooter then fled the parking lot in a vehicle.

“Clearly an execution-type homicide,” Small said.

Small said responding officers found the unresponsive victim lying in the parking lot with gunshot wounds to his head, chest and torso. He was pronounced dead at a hospital.

No suspect has been arrested and a motive wasn’t known. The person with the victim was not hurt, Small said. The victim’s name hasn’t been released.

Seventeen spent shell casings were found in the parking lot from a large-caliber semiautomatic weapon, Small said.

Police were talking to witnesses and reviewing other surveillance footage.