Sorry to resurrect an older thread:
But I think one of the dirty little secrets about increasing school violence, from Columbine to Sandy Hook Elementary and possibly Reynolds (I couldn't find a reliable source about Jared Padgett) is the side effects of SSRI's, Ritalin and the like. Some teenagers get suicidal, homicidal and psychotic on these drugs.

On the other hand school violence, and other violence, has always happened. They just didn't have access to rapid fire, high capacity, firearms in the past.

I will add that if you check out pics of Jared Lee Loughner (2011 shooting in Tucson) and Adam Lanza they look crazy. Jared Loughner's parents had contacted law enforcement and tried to get him committed repeatedly but nobody had the power to do something with him till after the shooting.
Adam Lanza's folks were divorced for 3 yrs prior to his shooting. Mom won custody with final say over Adam. She also owned a high capacity battle rifle with multiple clips, and other firearms, and had been taking little Adam to the range and teaching him how to shoot for years. She had expressed concerns and fears of Adam but kept the guns handy anyway. She paid with her life for her failure to institutionalize her son whom she knew had serious issues.