Um, excuse me Mr. Tainted one?
I sort of recall a special someone buying a tank forwards the end of Dead Air chapter 3 in that garage lot. This tank didn't just get crazy on the survivors though. Oh no, no, no. He went full blown INSANE on them! Before the round ended, I kinda remember you getting killed by a car, which ended up giving that special someone your achievement.
By the way, this special someone has a steam picture that looks like the one I'm using for the forums