someone from the Gung-ho gun was pointing a gun at Vash and the children. Vash was trying his best to de-escalate the situation by trying to talk some sense into that person. just as the person was about to shoot him and the children, Wolfwood (you) shot him in the head, causing that person to die.

Vash's eyebrows furrowed, he turned to look at you, and his eyes were beaming with anger and disappointment.

"What have you done!?! Why did you kill him!? He wasn't gonna shoot me!