From Comic Vine:
"The only survivor from a circus train wreck, a baby gorilla is found by Johnson, an elderly prospector who names him O’Neil and raises him.
Johnson teaches O'Neil how help him pan for gold, as well as how to cook, clean survive on his own in the Western wilderness, part of this involves O’Neil learning how to use a revolver, learning it so well he becomes a crack shot.
Life is tough but good for the pair, until one day while O'Neil is out hunting; Johnson is murdered for what the desperadoes believe he knows about “the great mother lode."
Getting back, O’Neil is able to tell who the men were who killed his friend Johnson by using his sense of smell, which is as good as a hound dogs.
Bent on vengeance O’Neil straps on a bandolier, holsters a Colt and starts to track down the six villains, though desert, swamp and over mountains, determined not to stop until the last murderer is dead.
He soon comes to be known as the feared Six-Gun Gorilla."