Smarter gun laws ? 
This guy bought a legal gun, then illegally modified it into a automatic. He had no history of mental illness and no criminal record. 
What "smart" gun law applies in his case ? No one over 63 allowed to buy a gun ? Change the Constitution? 
It is my opinion that if a person is hell bent on killing they will find a way. Blow people up with a bombs (he had explosives), drive a MAC truck full of fertilizer into the arena, poison the kool aid or water supply, fly a jet into the arena, start a fire in a crowded space and chain the doors shut, use a drone to spray anthrax over a crowd, or use rocks, garden hoes and machetes to kill with, like in Rwanda to kill 800,000 in 100 days ?
Through out history man has proven time again there is no limits to their imagination when it comes to killing in mass. Whether it is one mad man ordering genocide or one ingenious individual determined to avenge and vent their rage, they figure out a way. 
Could it be why people want guns ?