The Doctor stood where he was for a long moment gazing at the man he'd shot. His arm came down slowly to his side, the gun dangling loosely from his hand and finally falling to the ground from numb fingers.
Then time resumed its normal speed for him, and suddenly the room was full of the choked gasps of dying men. He watched Jack roll away from the Master, soaked with blood, but - well. If he died, he'd come back. He was getting that now. His eyes turned instead to the other Master, golden glow slowly spreading through him, and he fell to his knees, legs buckling, as he realised what this had cost them.