Methuen Police drill

Officers from the Methuen, Mass., police department carry training weapons as they search the halls of a school during a demonstration in Methuen, Tuesday, Nov. 11, 2014. School and police officials have unveiled a new system to detect and track a gunman that they say is the first in operation in a public school. (AP Photo/Charles Krupa)

Officers from the Methuen Police Department carry training weapons as they search the halls of a school during a demonstration in Methuen, Tuesday. AP

The active shooter detection system installed at a Methuen school recently and demonstrated on Tuesday was put in place free of charge to the city, but the company behind it says it has a few interested paying customers lined up.

Shooter Detection Systems (SDS) is the Rowley-based company that installed its Guardian Indoor Gunshot Detection system in a Methuen school. (The city isn’t releasing the name of the school.) The system’s sensors can detect the sound of a gunshot and alert authorities. It also allows them to track the shooter before entering the building. SDS’s technology was developed in tandem with DARPA and Raytheon.

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