The problem is that the United States is materially & institutionally constituted such that any such legislation that could've actually stopped this is probably neither passable, actionable, or effective.

Need I remind you that it is literally a core part of our Constitution (a thing you cannot change without a congressional super-majority, and which ostensibly overrules all other enacted laws) that says that you cannot federally ban gun-ownership.

Beyond that; in what world is US Law enforcement going to enforce those laws against Neo-Fascists? Maybe in the entirely hypothetical world in which you could democratically remove the 2nd Amendment, that could happen.

Do we live in that world?