Spasm

A lunatic wearing a black gasmask goes on a murderous rampage through a hiking trail, killing six people and leaving only one survivor. The survivor is blamed for the killings and is sent to a mental institution. Three years later he escapes, coincidentally around the same time sightings of a man in a black gasmask begin, and a man is found brutally mutilated. The gasmask man wants to finish the job and kill the person who escaped from him three years ago, and the survivor wants revenge for the brutal murder of his friend, and his sanity.