A threat sensing system is provided including, in some aspects, a plurality of threat sensing devices distributed throughout a school or facility, with each of the threat sensing devices comprising one or more acoustic sensors, one or more gas sensors, and a communication circuit or communication device configured to output sensor data to a system gateway. The system gateway is configured to receive and process the sensor data output from the threat sensing devices and determine whether the processed sensor data corresponds to one of a predetermined plurality of known threats (e.g., a gunshot) and, if so, to communicate the existence of the threat, the processed sensor information, and/or predetermined messaging information to one or more recipient devices (e.g., first responders, dispatchers).