This is just an awful situation. I am sorry for you OP, I hope you have someone in your life you can talk to if you need to. Suicide is a mental health issue, and another example of it being scary for mentally unstable people getting their hands on firearms. Can it be easily screened? no.
You can talk about selfishness, you can be angry at the guy... But the bigger issue is that he obviously had a lot of problems and saw no other way out.
The lesson to be learned? Are there any people in your life/scope of influence that maybe need a friend? Maybe if this guy had a community, a place to belong, a buddy to talk to, he wouldn't have done this.
Bad for guns, bad for the range, bad for the OP and other people that were there... worst for this guy and his family.