Night hysterics is a considerably more violent form of sleepwalking. During a night hysterics episode, sufferers essentially go insane for a couple of minutes. People sharing a room with anyone with night hysterics have a 50/50 chance of getting stabbed.
Famous sufferers include P.J. Benedict of Old Skull. Benedict almost murdered Lenny White, the bassist from Return to Forever, with a chainsaw one night. Interestingly, Benedict had never operated a chainsaw before and wasn't even sure where it came from. The cause of night hysterics is unknown, but Benedict suspects magic might be involved.