Police say a man trying to stop another man from beating a woman in a crowded San Antonio parking lot has been shot dead and a bystander has been critically wounded.

The shooting happened Friday afternoon outside a Wal-Mart store.

Police Chief William McManus says a man was assaulting a female companion when the other man drove up and demanded he stop. McManus says the attacker drew a handgun and fired at the man, killing him and critically wounding a female bystander.

A woman in the vehicle with the man who was shot was injured by shattered glass.

McManus says the beaten woman escaped and a police helicopter followed the shooter's vehicle for 10 miles before his arrest.