I did a bit of investigating and this fellow was selling guns illegally by laws I'm familiar with. It still does not justify the raid or the shooting, should have been a knock at the door during normal times.
He bought and resold guns as a "hobby" on the weekends without a FFL or doing background checks on the individuals he was selling to. So, he was in this for profit which fits the definition of a firearms dealer. These were not old firearms either, not old hunting guns or military surplus collectibles, they were mostly handguns, Glocks, Berettas and FR-16 pistols, whatever they are. Many multiples of the same model.
So he wasn't a collector replacing his collection or selling off unwanted guns, he was filling out the forms stating the firearm was for his use and then turning around and reselling it. Half a dozen of these guns were recovered from criminals although none were used in a crime.
It's a mixed bag, these laws are vague, the government is claiming the this is an example of "gun show loophole" but there is no loophole, he was breaking the law. He was purposely selling guns for profit which requires him to have a license and conduct background checks. This has basically been public knowledge and in place since the Obama administration. Biden simply made it even more restrictive and vague. Now anyone selling a firearm could be considered to be doing it for profit, you are considered guilty until proven innocent.