yea its a massive glitch 3arc didn't patch, its called "dead man glitch", i got one from cross map on villa, and i was pissed my one and only crossmap was a glitch X(
Call me crazy but i think i saw another video similar to this, but where the guy was shot. He was shot, then he respawned, and right as he did, the guy knifed his dead body and it literally spawn killed him..
EDIT: Yes! Here it is. Its #3 (2:30) in this video.
Me and my friends were testing it in a private match, and it seems to only work if you hit the dead body exactly when they spawn. I'd say you have like a 10% chance of actually killing him.