Preventing tragedys like VT, time to control violent videos / TV for young kids?

Kids in my PRESCHOOL cl watch horror films, one boy plays Freddy Krueger all the time. Another child only responds agressively to a negative action against him (even if a child accidently bumped into him). He just thinks kids are out to get him. he is a big video gamer, loves Deer Hunter and other violent games. He started games at 3 yrs old (and last year he hit all the time). Parents say thats what their kids like, and it causes no harm. They talk w/ their kids about it, and their kdis understand it is fake. But.... in the clroom I see the aggressive behavior, the anti-social behaviors, the lack of interest in school work. The kids say the games we play in cl are for babies. The kids have great difficulty playing in a 'nice' socially-acceptable way. They just want to hit, play kill, push, ect. They just can't figure out fun games that don't involve agression. So, in a few years, what will they be doing ??????