They are calling it a 'secret weapon' against intruders in schools: fog machines.
One school in Indiana is testing a number of security systems integrated together it boasts make it "The Safest School in America".
The system is composed of LEO monitored video surveillance, door lockdown fobs, 'bullet resistent' doors, and drills that evacuate students away from doors.
The video piece below demos the system named Net Talon. Details about the equipment being used are thin, but the reporter does say the system cost $400,000. In the clip below, a national morning news reporter is playing 'active shooter':