Only because they have easy access to guns. Every mass shooter I've heard either purchased their weapons legally or they were in the home after being purchased legally. (Think Columbine and Sandy Hook as two examples)
Exactly why real Americans voted out that potential dictator (Hmmm: the NRA supports a fascist dictator. Imagine that) That's right. The camps were approved under Donald Trump's reign of terrorism. That's why the pandemic hasn't ended, and our death toll from it is well over 1 million. (Heck we're still losing a couple hundred people a day)
Now, if the NRA is so great, why haven't they come up with a feasible solution. Best one offered is to have any gun purchaser have a mental evaluation done first.
Did they work? Let's see: COVID Deaths per million. OZ? 324 deaths per million. US? 3,081. Source: https://www.worldometers.info/coronavirus. If you can do simple math, you'll see that the US action to COVID was about 10 worse. Hell, India with over 4 times the US population had about 373 deaths per million.
Right, and where does Mexico get their guns. Smuggled in from the US. That's why Chicago, with some of the strictest gun laws in the US, has such a problem. Any gangbanger can buy a gun on the black market for a couple hundred. Strawman purchasers just take an afternoon drive over to Indiana, buy some guns, and by dinner time, have not only returned home, but also sold half of their recent inventory.
It's funny: I don't recall any mass shootings in the US, though, that involved illegally purchased guns. Closest would be the bozo that killed the kids at Sandy Hook.
If you read the second amendment, the reason the second clause was put in place was for local militia. Since the constitution was written, things have changed. The local militias have had the National Guard take their place. It's been around since before the US was the US. Okay, so let's make a law that only members of the militia own a gun.
The Buffalo shooter was a fascist, not a Marxist. Best you learn the difference. Who would fascists be? Hmmmmmm, they might try to storm a government building because they didn't like the fact that their candidate lost an election. They also happen to be very xenophobic, hating others because they are a different religion or race or even emigrated here, even legally, because that person was born somewhere else. You'll have to find better lies to spread.