This one was a known nutcase. The teen incident was just trying for attention in his warped mind, the same as his plan to kill as many ppl in the theater then walk to Wal-Mart and have a shoot out there and reloading from their stock.
Again, low self esteem with an psychotic mind and two military weapons makes a bad combination.
Law enforcement screwed up by not monitoring this nutcase since the 2009 incident. He should not have been allowed to buy any guns. Luckily, his family was watching him and did the right thing. Hope they really put him away this time for the protection of society - but since no one was killed (again) they may just write it off and give him another chance to kill a large number of ppl.