The only Convenient option is to kill him. If this was the scene in a movie, killing an unconscious enemy is something you expect the evil bad guys to do. The good guys go in, knock people out(and sometimes tie them up), shoot people who are actively shooting at them, rescue the damsel, and escapes with the damsel.
Picture this: Group of heroes is breaking into a drug dealers mansion. They capture a guard and force him to unlock some doors. When some other guards approach he shouts out. Someone knocks the guard out. You know what Doesn't happen next? They don't execute that unconscious guard. They might hit him again to make sure he's still knocked out by the time they leave. Willfully executing an unarmed, unconscious person is what the evil guys do.