This is why the US has fairly loose gun laws. Historically governments in the US were quite tolerant of vigilante violence against opposition to laws and social norms, such as racism and misogyny. It allowed the government and police to technically keep their hands clean while letting others do the dirty work. On occassion they would arrest and charge a few of them, but by and large most of them went unpunished. With mass shooters they will of course never see the light of day again (if arrested) but in secret they will love their actions.