He spends MORE time looking for the 'goodies'(helicopters/airplanes/etc) than in the killing stuff. And he won't do any 'killing stuff' when his little sisters are watching him play. ALSO, they are NOT ALLOWED to touch his game systems unless he's there to supervise what they play. (HIS rules)
He's a 'mean' big brother. Just ask the girls!
Not to tell you how to raise your kids, but you should read this to see the game your kid is playing:
http://www.answers.com/topic/grand-theft-auto-3