Studies have shown that anabolic steroids increases aggression, along with many other drugs. Studies have further shown that these aggressive tendencies may stay elevated long after the cessation of AAS use.
There are days where many events will make us more aggressive, just by human nature. My God, driving to and from work makes me want to kill someone almost every day, with only the stimulus of caffeine in my body. How you handle yourself and react to these daily events without any stimulus will only be prolificated with the use of AAS. So, if you cannot control your temper on a normal basis, and you are naturally an aggressive person, you will be just that much more aggressive and out of control. If you are a passive person, most AAS with the supposed exception of a few (as in Halo and Cheque drops), you many not even notice any increase in aggression. It is my guess that the average gym goer that is willing to subject themselves to intravenous injection AAS, is a naturally more aggressive person to start with.