The problem I see is that all the gun control laws in the world won't change a damn thing until American culture grows the fuck up and stops thinking that violence is the way to deal with problems. Not automatically demonizing someone who thinks differently than you do would be a good start as would teaching that there doesn't have to be a winner and a loser in every-damn-thing.
To use the drinking and driving example, we didn't ban alcohol to solve the problem. We made the consequences for doing it worse and we went to great lengths to make it uncool and unnecessary and not just turn a blind eye to it. We had to shift the cultural paradigm, and we're still only in the middle of doing it.
This guy was born and raised in America. He's American made. Period. To think he started hating fags and grabbed a gun just because someone from the country his parents came from (or whatever the excuse of the day is) told him to is delusional. Somebody whispered in his ear. It agreed with what his American upbringing had already taught him. That's why 50 people are dead.
I disagree with your notion of a cultural paradigm shift. People didn't automatically stop drinking and driving, and indeed people still do so today. What happened was people started going to prison for drinking and driving, seeing massive hikes in their car insurance, held liable for murders they committed, and in some instances banned from driving for life. Sure, we hear those numbers that 50% of all highway fatalities are caused by alcohol, and that impacts us, but the government was also using a pretty big stick to beat people who did not learn to comply with the law, which shifted our collective thinking in both a socially conscious way and an "I don't want to be caught breaking the law" way.
What is more, the government was free to collect highway data to learn how to reduce highway fatalities (both involving alcohol and not). Because of that, the government decided that 0.08 was a good limit, they created Dram Shop liability, they re-worked the way that highways were designed, and reduced speed limits. All of these simple solutions saved lives and the only really "control" on alcohol was that the age was raised from 18 to 21. But yet, we can't even gather data on gern violence in this country because the NRA has effectively shut down government and academic research into the area, so that the NRA's research (or foreign/intergovernmental organizations) are all that remain. Basic research into this area would go a long way into making minor policies that could keep bad people from having gerns that wouldn't affect Joe Six-Pack who goes hunting with his boy on Saturday. Having the data might show that 5% of shootings are done by domestic partners with a history of abuse (simple answer, ban domestic abusers from owning gerns) or 10% of shootings are done by people with a history of violent crimes (simple answer, ban those who commit violent crimes from owning gerns), or most mass shootings occur within a week after the lone wolf buys a gern (simple answer, longer wait periods), or from those purchased on the black market (simple answer, registry and background checks, as well as harsher straw purchaser laws). There is also keeping those off the terrorist watchlist from buying gerns (and since the government monitors ricin, planes, and explosives, mass shootings are the new M.O. of terrorists, definitely domestic and most likely foreign). None of these would affect a person's right to buy and own a firearm (unless you fall into one of these categories, or you really believe these people should be armed), but all would have a real effect on REDUCING gern violence. That's the key point, it's not about stopping gern violence altogether, but if we can cut it in half, that is a huge net win because that means 15,000 people are alive who otherwise wouldn't be (and the Australia case study is informative in this area, after it's absolute gern ban, it saw a precipitous decline in violence overall, indicating that these people committing gern crimes not move onto other weapons like knives and cars). And of course, there is the ever-persisting issue of gerns and suicide (which studies show is curbed drastically with waiting periods).
Finally, a big reason that our culture is so "yay gerns" is the NRA. They have convinced us that every democratic politician is out to steal yer gerns in an effort to whip up votes for Republicans, whipping people into a frenzy and thinking that they're gonna be like Han Solo and Luke Skywalker and use said gerns to overthrow the tyrannical government. Gern manufacturers have repeated exploited a toxic masculinity (almost a thin-skinned and fragile masculinity) in advertisements to sell gerns ("your man card has been renewed"). Some ads even equate gerns to toys like barbie dolls in which you "must buy all the accessories." Or the trope surrounding open/concealed carry, that you're somehow gonna shoot the bad-guy before he shoots you, as though you are John Wayne in the wild, wild west. The reason our culture is so backwards on gerns is because the NRA and gern manufacturers created these advertisements that push their views of gerns that play into people's fantasies while we have no sensible policy against which to push back. People can be as reckless or stupid as they want with gerns, and unless they break a crime that is facially neutral towards gerns, they probably will not be arrested.