Last Disciple not dying...bug?!

Hi,

(Edit: I am playing the game on PC)

I am in act 3, doing a sabotage side mission. I have to open the gate. I have downed the last disciple but he is just not dying, I have executed him, shot the hell out of him but he is just kneeling there (lying flat after execution) but his HP is stuck at 1 and he is not dying. Game keeps telling me that no. of enemies remaining is 1 so i can’t open the gate.

I have tried saving to main menu and even exiting the game and then reloading / continuing but its not working.

Does anyone know how to get past it without aborting / restarting the mission? is there a file or a console mode that i can tinker with?