Interesting that this thread appeared before the Atlanta one had even dropped off the first page.
According to this site
Gun Violence Archive (GVA) is a not for profit corporation formed in 2013 to provide free online public access to accurate information about gun-related violence in the United States. GVA will collect and check for accuracy, comprehensive information about gun-related violence in the U.S. and...
www.gunviolencearchive.org
there have been over 100 mass-shootings in the US so far in 2021. More than half-a-dozen occurred in between the Atlanta and Boulder ones that got threads on here. To cover them would probably require its own sub-forum.
Though it seems they are defining 'mass shooting' a little more widely than what gets considered sufficient to produce a thread on here, as most of those had multiple people shot, but only one or two fatalities.