Armed with pepper spray and capable of tackling: the new 'guardian angels' to combat school shootings in the U.S.

Austin-based Mithril Defense is preparing a pilot program using nonlethal drones to respond to school shootings in at least nine schools across Georgia, Florida and Colorado.

Teachers would trigger an alert, and remote operators would control drones equipped with lights, sirens, pepper gel or pepper spray; the drones could even ram an attacker.

The proposal is drawing concern over false alarms, communication latency and the risk of injuring innocent students or police officers.

The plan highlights how U.S. school security is increasingly leaning on technology, while raising new questions about identification errors and excessive force.