R.S.
As soon as the blaming starts, let him know from now on it's not ok and he will need to go to his room if he "blames on others". You can try to explain to him how and why he should take responsibility for his actions. If you don't address that behavior now and for as long as it takes to get through to him, he will believe it and he needs to start taking responsibility for his actions now. It's a lesson that might take some time for him to get. He sounds like he might be very stubborn, but don't give in. Take his behavior away from the family focus instead of giving attention to it. When he's been in his room awhile you might give him the opportunity to talk about what made him mad and really listen giving him the chance to express his feelings in an appropriate way. Never give him ice cream or any treat when he is trying to bribe you to be good. He needs to be good without any rewards. On the other hand an occasional treat out of the blue, when you want to give it is ok.