breh, you are focusing on the least important part of this. a chinese lunatic stabbed 22 kids and none of them died, his craziness, though tragic and as large as today's shooter, was not lethal. the shooter had better equipment for carrying out a massacre. that is the defining issue.
....if somebody snaps and wants people dead he will find a way. Which is why i brought up the issue of bomb making. Sure it doesnt happen often, but whos to say it wouldnt if guns were suddenly "harder" to come by. Youre using the chinese dude as an example..thats cool. But what about The Unabomber..Timothy McVeigh.
The mental state drives someone to commit an atrocity like this. The tools they use for it vary, but the root cause is theyre fukking nuts in lamens terms.