The gun was retrieved from Pretti BEFORE the shots were fired. The person who retrieved the gun did NOT PROPERLY COMMUNICATE that he had secured the weapon-- he should have been SCREAMING that the weapon was secured-- repeatedly. That lack of Key communication in those 2 seconds is the fatal failure, since it would have signaled to those agents subduing Pretti that he no longer was armed. The other factor that cannot be ignored: the horrible idea that if you are a "protester"-- it's OK to disregard commands by law enforcement-- ESPECIALLY true when you are carrying a concealed weapon. So-- a trifecta of stupid was responsible for that death.
Pro tip: Just don't "aggressively" interfere. "Kind of" interfering is okay. If you are manhandled then by all means, resist so you don't look like a pussy. Any questions, ask Alex.