Les was one of the grave robbers appearing in Tommy Jarvis' nightmare in the opening of Friday the 13th: A New Beginning.
Biography
Les' death
Along with his buddy Neil, he digs up the grave of Jason Voorhees in the middle of a rainstorm, while Tommy watches. When they get the coffin open, they marvel at the worm-eaten corpse. Jason suddenly springs to life and stabs Neil with a machete before killing Les with a screwdriver in the throat.
As the entire thing is revealed as a dream sequence, it's highly possible that he never existed in reality.