See what he did there? Because the shooter was stopped by law enforcement in a shootout, he’s sarcastically offering thanks to civilians with guns. “You know who you are. Thanks a million.” Get it?? IT’S FUNNY BECAUSE THEY DON’T EXIST.
That’s the joke Swalwell made. That’s the snarky sarcastic jab he opted for in the wake of human suffering. Because that’s what he really thinks, you see. He mocks the idea that a civilian with a gun could pull a trigger and shoot a bad guy.
And the reason isn’t because he thinks the bad guys are very dangerous, he is saying that people who own guns are all bad guys. It’s not just a joke that there weren’t any civilians specifically intervening on Saturday. No, his premise is that there is no such thing as a good guy with a gun because good guys don’t have guns.