Dealing with aggresiveness

I have a 3 yr old dcb who has been with me for about 18 months. In the past he has been VERY active and sometimes gets almost manic in his behavior. The past couple of weeks he has become very aggressive,( and even destructive) in my care and with the other children around us. Yesterday at a playgroup he purposely ran into another 3 yr old with a push car, proceeded to run over his hand when the child was knocked down, and then at the end of group during tidy up he was throwing toys at one of the other adults! I was mortified. He was removed from final circle time but didn't seem to care.
I spoke to mom and she is willing to take privileges away but I am concerned for the safety of the others in my care. Is this a stage? Does anyone have advice other than removing him from play to help deal with this. I only have 1 year left with him and don't love the thought of losing him but, he will not be allowed to abuse the other kids in my care (or anyone else).

Chances are with a child who is hyperactive and even sometimes aggressive, you will catch more flies with honey than with vinegar. Positive reinforcement works wonders for kids like this. That being said, it is still absolutely unacceptable for him to hurt other people. Discipline the poor behaviour, but reward, reward, reward the good. It's a long, slow, sometimes painful process, but children with difficulties like this need to learn that good attention is so much better than negative attention.

I know positive reinforcement is the buzzword of the day but I'm old school. I believe in a stern voice and sending a clear message when behaviour is unacceptable and a short timeout with me sitting beside the child talking to them about the problem so they learn and understand. Then they give out a hug and say sorry to the person they offended. I also believe in getting on top of this kind of behaviour immediately and staying on top of it and making sure the parents do the same at home. Of course I have a serious talk with the parents every day about everything that's happening too and take any of their suggestions possible.

Praise and rewards are doled out all the time at my daycare but only for good behaviour. I don't mean to offend anyone, I just can't wrap my mind around people who don't make it clear to their child that bad behaviour will absolutely not be tolerated.