Your friend was probably having a bad trip and didn't know what he was doing. Someone i know went completely crazy and threw a skateboard through a moving cars windscreen. He then proceeded to beat up the people in it when they got out. He normally seems rather timid too. I think he's got some real issues that come out when he's on shrooms though - the time he did them before he said he had a complete identity crisis and almost stabbed his friend. This sort of behaviour is pretty uncommon though and as long as youre a stable, non-violent person it's rather unlikely. In my experience, mushrooms are generally a very peaceful drug unlike drugs like alcohol and cocaine which do incite violence in a lot of people.