The rage fist has been observed to be manifested when directly provoked, physically or verbally, but is in no way premeditated. Much like instinct, it is a reflex attack, done out of haste or, as noted, out of Rage.
A direct hit has been known to not break, but *shatter* human bone, or permanently impair organ function. psychological effects have not been determined.
The parts of the body most vulnerable to the Rage Fist are the Sternum, the diaphragm, and the face. Care should be taken to avoid blows to the back, as paralysis is a possibility.
Inspector: "This man was not the victim."
CSI: "How do you know that?"
Inspector: "It's the way the face is concave. It's not like any other blunt force trauma, bone is smashed into bone here. This was done out of self-defense, and only the Devil knows what this man did to deserve this."
--overheard conversation at undisclosed crime scene.