Fact: The Aurora shooter told his psychiatrist that he had homicidal intentions. She did nothing. Fact: One of the Columbine kids was on psychotropic meds and was under investigation by the Jefferson County Sheriff for harassing one of his female classmates. The case was good, but the DA did nothing. Loughner, Lanza and the Virginia Tech shooter also exhibited dangerous behavior, which was ignored. You're right, the stabbing in Texas could have turned out much different had he been armed, regardless of the size of his magazines. The guy at VT had 10 round mags. The sound of gunfire might have brought police or an armed citizen into the fight sooner, and ended it. Hard to say.