>Improving police reaction time may save lives. Yes, but the reaction time is "after" the alarm, the point I was trying to make is that this surveillance/weapo

>Improving police reaction time may save lives. Yes, but the reaction time is "after" the alarm, the point I was trying to make is that this surveillance/weapon recognition approach may trigger the alarm earlier (of a couple minutes, maybe 5) but if the reaction time is in the tens of minutes range, it would make no particular difference in the actual outcome as all the shooting will happen anyway before the police can arrive. About the trust on the system, it's tricky business, as always, the amount of false positives need to be reduced to 0 or next to 0 to gain trust, and it is very unlikely, besides the errors of the system, like innocent maintenance people - say - plumbers or electricians carrying pipes or tubes, or some power drills, etc. (let alone carpenters with nail guns) I would bet that the new rage among the school kids would be finding perfectly legal items (let's say for the sake of reasoning antennas, cactuses, umbrellas) that would triggger the alarm, just for the fun of it. Good point about alternative "distracting" means (lighting colours, strobe lights etc.) but again, when (hypothetically) such a system will be installed I doubt that it can avoid daily, weekly or monthly false alarms and after a given number of them happens, usually the system is disabled or - if possible - set to very low (ineffective in practice) sensitiveness.