It appears from the video that the shooter’s primary weapon (on the first floor) was a KelTec Sub2000 Carbine Rifle in 9mm https://www.keltecweapons.com/firearm/rifles/sub2000/
The other “assault weapon” carried was a generic AR-15-style pistol - most likely a Palmetto State Armory model with a 10.5 inch barrel and a “pistol brace” https://palmettostatearmory.com/psa-10-5-carbine-length-5-56-nato-1-7-nitride-9-lightweight-m-lok-moe-ept-sba3-pistol-5165449599.html
The handgun is a Smith & Wesson M&P 9 Shield EZ with a manual thumb safety. https://www.smith-wesson.com/product/m-p-9-shield-ez-truglo-tritium-pro-night-sights-manual-thumb-safety
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Pictures of the arms here:
https://freerepublic.com/focus/chat/4140422/posts?page=1053#1053