"Resentment" is what was reported earlier as the motive. Maybe it causes a conflict of interest for the US military to send muslim-americans into battle against muslims?
Is that what this is about?
Muslim terrorists infiltrated as American baggage handlers, students, professors, taxi drivers, shop keepers, etc.
It's not too much of a stretch to think they've infiltrated the U.S. Army.
And that's horrific.