Chicago and Mobile, Alabama, are cutting ties with ShotSpotter, the controversial gunshot detection company — but the sensors that notify police about shootings probably aren’t going anywhere, according to a new report from Wired and South Side Weekly. 

Internal ShotSpotter emails reviewed by Wired and South Side Weekly reveal that the company hasn’t removed its sensors from other cities that have ended their contracts, including San Diego, California, and San Antonio, Texas. Per the report, ShotSpotter doesn’t sell its sensors but instead the software that alerts police that a shooting may have taken place. After a city’s contract with ShotSpotter lapses, the sensors occasionally remain installed. In some instances, police continue relying on ShotSpotter’s technology even after cities end their contracts with the company.

According to CNN, ShotSpotter puts 15 to 20 sensors per square mile. The sensors, which are often affixed to light poles, include a microphone, a GPS system, and memory processing.

An October 2023 email sent to ShotSpotter employee John Fountain suggests the company’s technology remains active even after contracts have lapsed. In the email, an unknown sender suggested addressing a sensor shortage in a city with an existing contract by transferring sensors over from an inactive market. “Last time we looked to remove sensors from an old coverage area I know Clark flipped out since we still work with police using those sensors (which I did not know),” wrote the sender, referring to Clark Dunson, the director of systems engineering at SoundThinking. (ShotSpotter changed its name to SoundThinking in 2023.) SoundThinking did not immediately respond to The Verge’s request for comment.

Another email, sent to Fountain in December 2022, said there were a “few hundred sensors still installed” in San Diego and that the sensors themselves were “active even if the market isn’t.” In an internal email sent eight months later, Dunson said that a ShotSpotter tech-support engineer was working with the San Diego and San Antonio police departments, “giving test alerts and tracking down detections for them.” San Antonio’s ShotSpotter contract had expired in 2017; San Diego pulled its contract in 2021.

The emails raise questions about whether the end of Chicago’s ShotSpotter contract will actually change much. Though Chicago’s contract expired on February 16th, the city won’t decommission the sensors until September 22nd. Earlier this week, one of the more than 2,500 ShotSpotter sensors located throughout the city alerted Chicago police to the fatal shooting of an officer, CBS News reported.