Well, there are some additional factors. 

What did this man get from committing this act? He believed he was going to Heaven. As laid out in the Quran, dying in the holy war to spread Islam is the only sure-fire way to get into Heaven. You can be a good person, true to the Islamic faith, but if Allah is having a bad day when you kick the bucket, he can still press the Hell button.

By dying in this manner, it is incumbent upon Allah to let him into Heaven. Allah owes him a solid, as per the Quran.