I burned a man.
What made you decide to burn a man?
I don't know, I just took a lighter and lit his hair on fire.
You should never purposefully cause other people harm. Setting someone's hair on fire is very dangerous and can kill them. You should seek help for having the urge to do such things, and resist the urge next time instead of giving in.
It was fun.
The fact that you found it fun to hurt a person like this is very troubling. You have to look at the reasons behind you wanting to hurt people like this.