You have to look at what caused his outburst. It may not have been something that actually happened in the class that provoked his behaviour, but the straw that broke the camels back.
Things to think about:
Was the lesson first thing? If so he could have had a bad night/ row with family
Was lesson after play/lunch? If so he may have been wound up by another child or had a lunch that may have made him hyper?
These things do happen frequently, try to help the child and not reflect on his behaviour from one point in time.
Good luck
