Shooting At Ft.Hood

[Husar]

Troubled by harasment
[...]
Just why he radicalised, became susceptible to it, seems the more interesting question.

Think about it, you sympathise with the people your own organisation is killing, yet you are loyal to your organisation, try to help it etc. Nonetheless members of your own organisation are harassing you because of your connection to the people they are fighting against. The link in the OP also mentioned that he was apparently targeting people he knew, perhaps those who were harassing him?
Looks like he was in the middle but forced to take a side, now what sort of idiot would take the side of the guys who are harassing him because of his beliefs or skin colour?

If he was some jihadist nutjob who was dangerous from the start then congrats to the US army for being idiotic enough to hire him and letting him take care of their wounded.