I'm not giving him excuses or a pass for killing police officers at all.
But it sounds as if the guy was dealt a really bad hand (kicked out of the military for stealing a very close female friend's underwear).
http://nypost.com/2016/07/15/dallas-sniper-was-sent-home-from-afghanistan-amid-claims-he-stole-soldiers-panties/
I think the woman who turned him in is full of shit. His mother claims his friend was having a relationship with someone of a higher rank which her son knew about and that actually makes sense.
Makes me wonder if he had been treated fairly, would he have committed the crimes? Like I said, being treated badly isn't an excuse but it does sound as if he was thrown under a bus, humiliated and potentially had his career ended for something petty. From his young viewpoint, maybe he felt like he didn't have anything to lose at that point.
On a separate note, a friend of mine was pushed out of a helicopter at 1000 feet once they found out he was gay. From what I understand, none of the folks responsible were punished. But if you dare to steal underwear....