Warhead = 24, thats the Blamo-killer. kills things such as Purchase Terminals and AGT guns. Things thought to be undestroyable. He has the Pistol selected, so, unless the pistol is designed to do that in the server, he 100% certainly cheating.
Damage warnings in BIATCH are 100% positive, server side weapon mods can cause conflicts, but unless you see this message pop up fairly frequently then the guy is DEFINATELY cheating.
And, yes, hello Nune. I figured your prior experience with TK2 would have helped you a bit here...