This myth seems to come up in most Gus threads.
His two friends were accused of stealing cigarettes from the girl and her brother while they were bathing. The drunk girl was in his face screaming about it, since she knew Gus from before. He pushed her away. Then her brother started swinging at Gus but missed (he told the police that, but in the trial he changed it to that Gus hit him first). They wrestled on the ground and Gus got on top, headbutted him and yelled "have you had enough?".
Also this was 13 years ago.