Radio

Each guard has radio with him.

Trigger
A guard will turn on his radio upon hearing a gun sound or seeing an agent. It takes some time for a guard to turn on his radio, during which he cannot attack.

Outcome
He will turn off his radio after searching without finding anything. The alert level slightly rises after one guard turns off his radio.

If a guard is killed with radio on, his body will be instantly found. It is the same outcome as when a body is found.