Floyd won't be comparable. Floyd is mostly famous for being the straw that broke the camel's back. It's best view in context than as a single event. I'm not even sure comparing it to a private property owner works, since protecting a government is an entirely different category. Sommer is correct, though, that a private owner would be held to a lower standard. But that's true in general, and rightly so.
There will be a point at which security would have to use lethal force, and it's not like people were blind to that fact. The question as to why there weren't more non-lethal dispersion efforts being used upstream is a failure of the entire system than a damnation of the specific shooter. Two AR-15s are in that hallway nearly immediately, but there's no teargas in the hallway?
The Hollywood in me asks where the warning shot was, but the real world doesn't have warning shots.
It's an insurrectionist disguised as a civilian. That's a dangerous job, and people volunteer for it.