Many of us have video cameras independent of cell phones. No “kill switch” effect there. If you’re deliberately joining such an incident, you’ll likely have time to grab it (or even buy one quick from darn near any electronics store, Walmart included) - if only for the much better optical zoom, as anything interesting may easily be too far for a cell phone camera to record well.
Need private network and secure link out of controlled area to document the play-by-play.