Why background checks do not stymie mass shooters. The vast majority do not have disqualifying records, and "universal" requirements are easily evaded.-
[reason.com]

A New York Times story about the NIJ study illustrates the sort of magical thinking that is required to believe that expanding background-check requirements is an effective way to prevent mass shootings. After explaining why background checks do not stymie the perpetrators of such crimes, the Times paraphrases a gun control activist who "said the only way to stop mass killings was to enact strengthened universal federal background checks, to compensate for the wide variation in state and local laws." The problem is not a lack of uniformity; it is the inherent limitations of background-check requirements.

Speaking of magical thinking, Democrats predictably latched onto the Buffalo massacre as a pretext to once again demand a renewed and expanded federal "assault weapon" ban. Never mind that New York has such a law, which demonstrably did not prevent or mitigate this mass shooting. Given the arbitrary distinctions drawn by such bans, they cannot reasonably be expected to have any meaningful effect on such crimes.