NEW YORK (CBSNewYork) – The high-tech experiment to track the sound of gunfire in certain parts of Brooklyn and the Bronx has alerted the police to dozens of shootings that they say they’d never have known about otherwise.

On March 18, Deputy Commissioner Jessica Tisch said the ShotSpotter lit up in Brownsville, Brooklyn.

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“The shot count here remarkably was 23 rounds,” she said.

The system led officers to a building where Chief of Detectives Bob Boyce said they found the shell casings on the roof.

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“A very dangerous weapon, 9mm fully automatic machine pistol,” he said.

It’s a shooting he said they’d never have known about; nobody called 911.

As WCBS 880’s Alex Silverman reported, of the 55 incidents picked up on Shotspotter, police say only 12 were called in.

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It could eventually change the way the NYPD counts shootings. Right now, they shootings are only reported publicly if there’s a victim, Silverman reported.