J.T.
I think definitely hitting with a bat probably warrants a call to the police-you're in the best position to determine the severity of it, but it sure sounds bad and terribly inappropriate. (Of course, depending on whether it was a plastic t-ball bat vs. an aluminum or wooden bat...) In any event, you might also try to help your son find other ways to deal with it: Can you invite the nice kids over for pizza or some other kind of activity in your home or to some other activity? Maybe the other parents would respond to this as well and might also be interested in get togethers where these bullies are not involved. Sometimes the best solution is for the kids to be motivated to change their own behavior after they realize that no one wants to play with them (or the parents will see their kids being left out and take action to correct the inappropriate behavior).