If an intruder were to start shooting at a school, the new ShotSpotter system would not only detect the location of the shots, but also that it was fired from an automatic rifle. Small sensors placed in every room and common area of the school pick up every shot.
The alerts come into ShotSpotter's incident review center.
ShotSpotter President Ralph Clark says for police, time is of the essence.
"There's been two to three minutes before calls have been made to 911 and every minute really does count," he said.
Once police are notified the developing information hits police car computer screens instantly. Responding officers know exactly where to go and what they're up against.
"We can tell you how many rounds were fired and if it was multiple gunmen," ShotSpotter Vice President James Beldock said.
It's priceless lifesaving information, but it can also be pricey. It costs $15,000 to set up the sensors at each school, plus a $10,000 per year fee.
But former San Francisco Police Chief Tony Ribera equates this with the success of fire alarms and sprinklers in schools.
"In the last 25 years, with the exception of dormitory fires, no children have been killed in school fires," Ribera said.
Ribera and other police officials say the cost doesn't seem like much if it helps save lives.