My friend M. was thinking about solutions to prevent a recurrence of the Las Vegas shooting -- specific to what that guy did.
First, he said, there should be gunfire sensors on the outsides of the buildings. These have been around for a decade or so, and are used in London, for example. This would triangulate the sound of the shots and pinpoint the source. Once you know if they're coming from a certain building -- and this could happen very rapidly -- the hotel could have a dropdown "shade" that blocks the view from the windows. He wanted it to be a bulletproof thing that unrolled from the roof, but just a regular shade would interfere with a shooter's targeting people too.
I asked him if this sound-locating system could work while a street concert is taking place. (Waiting to see if he's got a fix for that.) .... He says yes, it can pick out the sound, and distinguish it from firecrackers and similar sounds. Only one thing, the Boomerang model "does not claim to be able to detect shots fired from firearms with sound suppressors."
The more he talked, the more I felt like we're living in Judge Dredd territory or something. Warfare in the streets.