Does anybody know how to tap into your subconscious?

I was with a small group of friends at the mall and while we were there 2 out of the 5 friends that were there were doing things, and later they had no idea that they did it. A few days later one of them got into a fight and i think he tapped into his subconscious,blacked out, or went berserk, because in the end even though he beat the guy up badly, even when the guy was on the ground he still hit him a few more times. so when we left the did not say a word when i talked to him in the car,until about five minutes later he had no idea what happened.(note this is not the first time things like this have happened) so i wanted to know if this is some sort of defense mechanism to protect him. (could anybody do this; because i myself have had a moment where i didn't remember anything so i wanted to know if there was a way to control it on command.)