It looks like he just reflexively grabs it without thinking how to grab it safely. Likely also implies that the safety was off on it.
Yeah, it goes off when he grabs it and not when it hits the ground.
The Plaxico (or Lil Wayne) case is different in that NYC has some really strict gun laws where Denver does not. You don't even have to register firearms here and I don't believe we have any laws about carrying in a bar or club either. Of course, that's all moot because the FBI guy shot someone but possession alone is not a crime here unless you're a felon or otherwise restricted from gun ownership