I don't understand what you are looking for Eddie? What kind of answer do you want?

Laws don't prevent anything. Murder still happens. Laws and their associated punishments are repercussions for breaking said laws (detriment to society). Most people don't break major laws because A) most people are good in nature and B) most people don't want to face major repercussions (Don't want to due time? Don't do the crime!). It's a social contract - break it and pay the piper.

That still doesn't stop someone who is hell bent on breaking a law anyway. Murder is against the law, yet these shooters still shot because they don't care about breaking their contract with society. There is no such thing as "pre-crime" which preemptively prevents crime from happening to begin with. There is no "I pulled you over because I knew you would speed in the later future". Same thing applies to these shooter punks. Due process is a thing.