It's easy... you break into the victim's flat, and wait just behind the door with a machete. When the victim comes into their flat, slash violently at their neck area, several times if necessary. Make sure you're wearing cheap clothes that you're willing to burn, and have a change in a plastic bag in the bushes nearby, as well as a number of towels. In my experience, this always stops prank wars quickly, effectively,…
Geez tough crowd.