MANILA—The gunman who went on a deadly rampage at a metro Manila gaming complex was a Filipino gambling addict who had been recently barred from the country’s casinos, Philippine police said.

On Sunday, police identified Jessie Carlos as the assailant in an early Friday gun-and-arson attack at Resorts World Manila that left at least 36 casino guests and employees dead of suffocation from smoke.

Philippine President Rodrigo...