The head of a union representing the New York City Police Department has asked Google to deactivate a feature on the mobile app Waze that allows users to share the presence of police in real-time, New York Daily News reported.

The app claims to be the “world’s largest community-based traffic and navigation app,” and lets drivers share real-time traffic and road information – including the whereabouts of the police and speed traps. Its Google Play page says users can benefit from “community reported alerts including accidents, hazards, police, road closures, and more”.

In a letter to Google CEO Larry Page, Edward Mullins, head of the Sergeants Benevolent Association, said 28-year-old Ismaaiyl Brinsley had the app on his phone when he executed two cops. Mullins has also threatened legal action and wants to meet a Google official within 10 days.

“I don’t know if he was going to use the app and I’m not casting aspersions on Google for that. But how could they not know the atmosphere this creates by keeping it out there?” he wrote.

“Google must recognise that the police icon is just a tool that, like any other, can be used for good or bad purposes,” he added.

Google has not yet commented.

Previously, the National Sheriffs’ Association criticised the app for putting policemen in danger and for defeating the purpose of speed traps.