In particular, I watched
out for nightclubs. They were fun, but blocked exits ( so people can't sneak out without paying their check, or let friends in without paying the cover charge ) and overcrowding were serious concerns.
eg: The Cocoanut Grove Fire in Boston. Completely accidental. Just a greedy owner. "Numerous building code and safety violations."
Killed 492 people (which was 32 more than the building's authorized capacity) and injured hundreds more.
You go into a negligent situation like that now and add an Active Shooter, explosion, fire, ...
Saw this from Homeland Security and FBI,
Law Enforcement Vigilance and Caution Urged during Public and Political Eventshttps://info.publicintelligence.net/DHS-FBI-LawEnforcementVigilance.pdf
It goes into detail, and is worth a read for anyone interested in the subject.
What was that line from last century? "The bomber will always get through".
"I think it is well also for the man in the street to realise that there is no power on earth that can protect him from being bombed. Whatever people may tell him, the bomber will always get through
. The only defence is in offence, which means that you have to kill more women and children more quickly than the enemy if you want to save yourselves."
Edit to add:
Training children how to triage and treat shooting victims before Paramedics arrive,
New class for city kids: How to survive a shootinghttps://www.washingtonpost.com/national/new-class-for-city-kids-how-to-survive-a-shooting/2016/07/30/ebd1aaf2-3e29-11e6-84e8-1580c7db5275_story.html