Yes, exactly! He is solely and personally responsible, him alone. His ego and arrogance, combined with his pure hatred of anything decent, all combined to this event.
If he was of a clear, rational mind and thought he would have checked, rechecked, and checked again to see if the weapon was indeed loaded with either blanks or live rounds. Instead he picked the weapon up, pointed it at the woman, and pulled the trigger. Since he’s been an untouchable for all these years he didn’t think, he just acted out.