For a big hit series they have made it hard to keep up with the episodes but here is the gist as I see it.

There are two guys that have the ability to explode. The one you are talking about is a good guy and I wondered exactly the same thing. Hide in the desert FCS. There is no obvious answer but there are forces at work that will somehow see to it he is in NYC at the right time if they need him to explode there.

One is evil and would only explode on purpose if he believed he could regenerate afterward. If he can kill the cheerleader he will gain that ability.

So, the good guys (you need a program to keep up) are faced with two idividuals that can destroy NYC. One is evil and insane and would do it just for kicks. The other is good but is manipulated by various powerful forces.