He was portrayed by John DeSantis.
Incident On and Off a Mountain Road
A woman named Ellen travels down a mountain road where she collides with an abandoned car. Curious to see if its driver is around, Ellen goes out to investigate and discovers a trail of blood. This disturbing discovery leads to Ellen crossing paths with the demonic-appearing killer Moonface. While Ellen initially manages to delay Moonface from capturing her with tactics learned from her (abusive) survivalist husband, Moonface catches her off-guard and drags her away.
In Moonface's lair, Ellen awakens with a piece of jagged material in her shoulder, surrounded by corpses, and is greeted by the insane Buddy who seems to be an ally/cohort of Moonface. The deformed killer returns with another woman in tow (possibly the other driver) whom he straps to a table. Using a drill press connected to a barrage of loud noises, Moonface horrifically drills out the woman's eyes.
Buddy talks Ellen into using the material in her shoulder to pick the lock but then gives away her position. Moonface attacks her and she counterattacks with a piece of wood. Ellen throws Moonface through a window where he hangs supported only by a tearing blanket over a (now-revealed) waterfall outside Moonface's lair. When it gives away, Moonface plummets to his death. (It is revealed in a twist that Ellen had murdered her abusive husband and was taking his corpse out in the mountain area to dispose of. She uses Moonface's drill press to remove his eyes and stage it as though he was another of Moonface's victims. She then shoots Buddy and disappears.)
For the most part, Moonface's behavior was unknown except that he had a knack for terrorizing his victims (judging by the noise barrage connected to his power drill) and mutilation as evidenced by his actions towards the female victim Ellen witnesses. He also was mostly mute, save for his unusual habit of telling intended victims "Shhh".