Do you know that he didn’t take a gun safety course? For all we know, he could have had plenty of knowledge on how to safely handle a firearm and simply decided to ignore it for the sake of looking cool. The fact is that no amount of safety training can stop someone who decides to do something stupid.
I absolutely agree with your last point though. There should be extensive training in how to handle a firearm safely required before someone can buy a gun.
I prefer to use Main/Sub terminology. It also works without needing to change any acronyms.