I can't believe how many people have their heads in the sand on this one. "Too many mentally ill people"? I guess it's always easiest to blame the mentally ill instead of focusing on societies ills.
Economic strain, drugs, alcohol, keeping up with the Jones, etc are more likely to push someone over the edge to commit mass murder than mental illness. There are tons of seemingly normal people out there that on the verge, waiting for the other shoe to drop & the last straw to pluck, before they plunge into the abyss.