The New York Police Department’s newest crime fighter is a robotic dog. Several videos of the four-legged machine – built by Boston Dynamics – have gone viral in recent months. The latest spotting was on Monday (watch above).

“I ain’t never seen nothing like this in my life,” said a bystander.

The robot was deployed to a Manhattan housing project to help in a potential hostage situation, according to Gothamist, but its human handlers wound up resolving the situation without the new technology.

New Yorkers, including Rep. Alexandria Ocasio-Cortez, a Democrat, have expressed skepticism of the futuristic new policing tool. Last month, City Councilman Ben Kallos, another Dem, introduced legislation to ban the NYPD from using “weaponized” robots. The robotic dog is technically unarmed. Similar models from Boston Dynamics can open doors and are strong enough to help tow 18-wheelers.

On Wednesday, New York Mayor Bill de Blasio said, “I certainly share the concern that if in any way it’s unsettling to people, we should rethink the equation. So, I don’t know what is being done to test it. I’ll certainly talk to the Commissioner about it. I don’t want people to feel you know, that something is happening that they don’t know about. So, we’ll work that out.”

In February, the NYPD used the robot in a similar situation in the Bronx. Writing of that incident, which involved a kidnapping, The New York Times explains:

The police decided it was time to deploy Digidog, a 70-pound robotic dog with a loping gait, cameras and lights affixed to its frame, and a two-way communication system that allows the officer maneuvering it remotely to see and hear what is happening.

The police said the robot can see in the dark and assess how safe it is for officers to enter an apartment or building where there may be a threat.

In the case of the Bronx home invasion, the police said that Digidog helped the officers determine that there was no one inside. The police said they were still searching for the two men, who stole a cellphone and $2,000 in cash and used a hot iron to burn one of the victims.

“The NYPD has been using robots since the 1970s to save lives in hostage situations and hazmat incidents,” the NYPD tweeted in February. “This model of robot is being tested to evaluate its capabilities against other models in use by our Emergency Service Unit and Bomb Squad.”

The Massachusetts State Police were the first law enforcement agency to test out the robotic dog.