Slang Term for "Murderous Rage and Anger." The individual is out of control, irrational and violent. Often resulting in the death of others and themsleves. More rarely used to describe NPC's in some more violent video games.
Teens/Adults going into a McDonald's/hospital/school with extreme angst and mental problems start shooting up the place are "Mur-Rager's". Often a response to bullying, result of alcohol abuse and/or drug abuse
"They keep picking on me I'll go Mur-Raging on those a$$holes."
Non-player characters in many video games are "Mur-Ragers" having no other purpose but to maim, kill and destroy, even at the cost of their own existence.
"That drunken SOB butchered his whole family in a Mur-Rager."