> Shotspotter isn’t an AI though is it?

Shotspotter has been billed as a “system of sensors, software, AI and expert human review that accurately detects, locates and alerts police to gunfire”, and the company behind it (formerly “Shotspotter” was the company name, its recently been renamed “Soundthinking”) has a number of other AI-involved law enforcement products now, as well.

That's a layman explanation. ShotSpotter is likely a passive radar system. In recent years, you can combine signal processing and supervised learn (neuralnet) to get better direction-of-arrival estimations.