Sick **** continued to fire on people who were already clearly dead. Wouldn't surprise me if this loser was ex-military. The calmness and sheer detachment from human life he displayed while gunning people down was sickening.
Some have commented that his gun handling and approach didn't reflect proper military training. i.e. he was doing things that could have got him killed if he was in a real gun fight and not re-enacting the "No Russian" level from Modern Warfare 2.