Hello! Please remember that my responses are informational only, we are not establishing a therapeutic relationship.
I can imagine that you are extremely frustrated with his behavior!
Some four year olds are too young to be in time out unattended. Sometimes the parent has to take the time out with the child to help them truly stop moving.
The best resource I have for this behavior comes from Howard Glasser and his "Nurtured Heart approach. The website is http://www.difficultchild.com/
I think praise and time outs are excellent tools, however, it's very easy to not use them appropriate. Glasser, for example, shortens the time out significantly from the standard advice you will see elsewhere --because the point is lost and forgotten with long time outs. He tries to help parents make the link between "This behavior makes the fun stop," and the life only stops for as long as it takes for the child to realize what they did that caused the fun to stop.
The way he teaches how to use praise is a little different too --it's much more observational of small things the child is doing right, it's also not a "big deal," when it happens and it's done far more frequently than people typically do (I think we as parents naturally tend to give 4 criticisms for every 1 positive we give!)
I know that your four year old probably doesn't read, ;) but you might want to take a look at this book: My Book Full of Feelings: How to Control and React to the Size of your Emotions --you can read it and it might help you to understand emotions from a child's perspective.
Children have poor impulse control, and they cannot verbalize their emotions --hence they come out in behavior ---for some kids, obviously hitting and biting.
The point of the 2 resources above is to help you identify his emotion, help him to identify his emotion, teach him that he can have the emotion (but needs different behavior) and reinforce everything that's not this destructive behavior.
Please feel free to follow up ----