Joe fucked up his ONE job
He gets hired as a bodyguard.
Literally 15 minutes later he is incapacitated and his client gets killed.
I love this movie, but this initial fuckup is too much to be ignored like the scripts does.
They should have given Joe a better reason to be surprised and let Cory die, more unavoidable and not his fault, certainly better than picking up a cigarette from the floor.