You have prevention, detection, mitigation.
Prevention is blocked due to many issues, none of them logistics. Short answer, that resolution path is blocked.
Detection - How can you detect?
Embedded RFID or some other tagged indicator but much like RFID wallets that can be circumvented.
The key component to a gun, is the projectile. This idea is already trending in the discussions I see.
Again, you can't tag the projectile at the point of manufacture but perhaps you can detect its characteristics.
Idea - Open Source to detect gun/rifle shot with a high accuracy. This could get put in embedded systems or perhaps even android phones.
Better detection may allow for automatic reporting. It's a start.
Weapons fire is a high risk situation. How can you reduce the risk with preparation? How can you allow for mitigation?
We've all read stories of "sleep gas" and stun grenades but what options are there?
Idea - A device to neutralize a situation that can be deployed with minimal risk to the first responders. Risk equals delay.
Sound would seem to be the best vector for delivery. Any non-lethal (preferably non lasting side effects) is another tool in their tool kit.
Again an open source option seems best to me, because it could be deployed via cell phones or existing sound systems.
As much as we hate "Don't tase me brow" any option is better than none. In this case it could be an option for the DJ or business owner to deploy to
clear the building. There are no lethal words or sounds as yet, only volume/amplitude.
If SWAT is equipped with the appropriate counter it clears the playing field of non-actors.
Last out there idea (perhaps for synergy):
An automated robotic aggressive response. A targeting mechanism that returns fire (possibly non-lethal) for the source of gunfire. Again, projectile's
are mass produced and static in their design for near 100 years. Focus on the technical sticking points.
(Since I've been me for a long time I wouldn't be surprised if the above isn't already well on its way if I googled for it. My hope is for discussion not awards or kudo's. I.E., don't nitpick my ideas apart just riff on it please.)