@Tearsax He was never anything else. It's not as if he's been careful to avoid collateral damage or death in his rampage. The fact that he doesn't kill unnecessarily is almost incidental. If he needed to for his 'justice'? He would.
Admittedly, for this he has to make a big threat, and make it personal. I doubt he wants to have his aunt become a permanent hostage they use to control his behavior. If they believe his bluff/threat than he gets protection for his surviving family, and doesn't have to become a weapon of the US military.