I did expect this response (and I don't mean this sarcastically), a chap close to where I live had a similar thing happen to him.
He found some scrote breaking into his car http://www.itv.com/news/calendar/story/2013-07-22/have-a-go-hero-in-hospital/
He died of his injuries 2 weeks later. You cannot reason with these people, they may be armed, high on drugs/booze who knows.
I would have done exactly the same, fight or flight kicks in and sometimes there's nowhere to run.
If they tried to attack first what would you do, "please think about what your doing" chats just don't happen.
He has not lost it completely when he's tackled him because if he's manged to break bones then a strike with such force to someones heads would more the likely end them!