I don't think it's literally, "I need to have 'The Talk' with Little Timmy and tell him not to go on a rage killing spree when Little Susie spurns him." I think it's more spending time with your kid, being a good example, maintaining a stable home life, actually doing things with them (getting out there, not hanging out or sitting them in front of YouTube), keeping them active in after school sports and/or activities and doing whatever you can to minimize outside negative influences... "Right" and "Wrong" will come on its own from there.
In other news, a school district in Pennsylvania has found their solution to in-progress school shootings: a bucket of rocks in the classroom. I'm not making this up.
http://pix11.com/2018/03/23/students...ntendent-says/