Try doing behavior chart with him. Take a chart paper.. divide into 2 parts. For every acceptable behavior or even tiny success, put a star sticker. For every bad behaviour or unacceptable behavior put a 'cross' mark. And suppose if he gets 10/20 stars, tell him he will get a toy/ his fav. Food, etc.
Explain the behavior chart to your child.
Also, see a psychiatrist to rule out any other issues
Next Steps
seek Psychiatrist help