Before cop killer Ismaaiyl Brinsley ambushed two New York police officers last month, police said, he wrote on his Instagram: “I’m putting wings on pigs today. They take 1 of ours, let’s take 2 of theirs.” He apparently expressed support on social media for Michael Brown and Eric Garner, who were killed by police.

Brinsley also posted a screenshot from Waze, a navigation app that allows millions of users to help each other track traffic, road hazards, construction zones and the whereabouts of police officers watching for speeders, among other things. It’s immensely popular, particularly with people who spend a lot of time on interstates.

Investigators don’t think Brinsley used the app in his attack against NYPD officers Rafael Ramos and Wenjian Liu — partly because he threw out his cellphone more than two miles from the scene. But a Los Angeles police chief doesn’t buy it, and he fears the technology could aid others who want to hunt and kill cops. He’s not alone.

In a letter, Los Angeles Police Chief Charlie Beck urged Google, which owns the app, to disable the feature that warns drivers when police are close by.

Waze described how it works on its Web site.

After typing in their destination address, users just drive with the app open on their phone to passively contribute traffic and other road data, but they can also take a more active role by sharing road reports on accidents, police traps, or any other hazards along the way, helping to give other users in the area a ‘heads-up’ about what’s to come.  In addition to the local communities of drivers using the app, Waze is also home to an active community of online map editors who ensure that the data in their areas is as up-to-date as possible.

A driver who spots a construction crew, a stalled vehicle or a police car simply taps an icon on the app. The warning — in the form of a cartoonish symbol — then pops up on everyone else’s Waze map at the same location. Bluetooth enables voice notification to drivers as well, alerting them that a police car is up ahead.

There’s no way, however, to know whether police are awaiting speeders, aiding a disabled vehicle or doing something else. Sometimes, the patrol car is gone by the time the driver reaches the area. In any case, Beck said, it’s a safety concern.

“I am concerned about the safety of law enforcement officers and the community, and the potential for your Waze product to be misused by those with criminal intent,” he wrote to Google chief executive Larry Page, according to NBC Los Angeles. “I look forward to opening a dialogue with you as to how Google can prevent the future misuse of the Waze app to track law enforcement officers, thereby avoiding any future deaths or injury.

“I am confident your company did not intend the Waze app to be a means to allow those who wish to commit crimes to use the unwitting Waze community as their lookouts for the location of police officers.”

After Beck’s letter, sheriffs spoke at the National Sheriffs’ Association winter conference last week in Washington, D.C. One referenced the app as the “police stalker.”

“The police community needs to coordinate an effort to have the owner, Google, act like the responsible corporate citizen they have always been and remove this feature from the application even before any litigation or statutory action,” Sheriff Mike Brown from Bedford County, Va., said, according to the Associated Press. Brown is also the chairman of the association’s technology committee.

Southern California reserve Deputy Sheriff Sergio Kopelev brought the issue to Brown’s attention during a funeral for one of the fallen NYPD officers. He calls his attempt to ban the app’s feature his “personal jihad.”

Waze has since responded to concerns.

“These relationships keep citizens safe, promote faster emergency response and help alleviate traffic congestion,” Waze spokesman Julie Mossler said in a statement. “Police partners support Waze and its features, including reports of police presence, because most users tend to drive more carefully when they believe law enforcement is nearby.”

Google declined comment to the AP.

If the company did discontinue the police-tracking component, it wouldn’t be the first to do so. Amid pushback from from legislators, Nokia killed the sobriety-check tracking function from its Trapster app, the AP reported. The app was discontinued last year as Waze came to dominate.

But some law enforcement officers say they want their whereabouts known.

“We want to be seen,” San Jose Police Sgt. Heather Randol told the San Jose Mercury News. She said there’s a purpose to “being highly visible on patrol” — to reduce crime.

In fact, some say the app’s feature could even be called helpful.

“Someone is less likely to speed if they know a police officer is around the corner,” San Francisco Police spokesman Albie Esparza told the newspaper. “It also helps with public safety so people know where there is an officer to get help.”