It is pretty absurd the enemy is literally on the floor - and you can't kill it because the weak point is facing the opposite side.
You have to wait for it to come back alive to kill it? Really you can't just turn over the enemy and just shoot it?
Suggestion - ( for sake of easier programming than doing a full animation of ground executions )
When enemy is "downed" they get a new weak point on the entire chest. Front and back. Player shoots it and enemy is dead.
Later on you can probably swap it out with a head stomp or something to kill it.
Or the player just picks up the corpse ( transistion )to "force" enemy to stand" ) then continue with execution animation,