It's about a dirty old man who is a caretaker at a camp. No one likes him and so some campers decide to scare the wits out of him while he's sleeping. They do just that, and when he jusmps back in fright he knocks over a candle and burns alive. He gets out of the hospital and goes back to the camp for revenge. It came out in 1981 and it was Jason Alexander's first film (best known as George on Seinfeld). A typical slasher film, but Tom Savini does the effects and if you see the uncut version, it is WELL worth it. In fact, the best scene can be seen right here uncut!
http://www.imdb.com/title/tt0082118/videosites
Amazon.com used to sell it but I'm not sure if they do anymore. Check it out if you get the chance!