Police Commissioner Bill Bratton said cops are in “uncharted waters” following the shooting deaths of three officers in Baton Rouge, Louisiana, on Sunday.

Speaking on the CBS Evening News, Bratton recalled the killing of Officers Rafael Ramos and Wenjian Liu, who were gunned down while sitting in their patrol car. He said since then, the NYPD has focused on technology (being able to alert officers quickly if there is a threat) as well as community-police relations, which have been strained throughout the country.

“I think its quite clear that we are in perilous times — the country and the police profession,” Bratton said. “Policing in America is getting a lot more difficult.”

But Bratton added that cops have “stood up to” difficult situations in the past and “we will work very hard to stand up to them again.”

The sentiment comes after police officers citywide were told not to venture out alone.

“In light of the ongoing events in Baton Rouge, Louisiana, which has resulted in numerous Police Officers being shot, effective immediately and until further notice, all foot posts are to be assigned dual patrol,” according to a letter that went out to al city police officers. “There are to be no solo foot posts citywide. All uniform members of service shall arrive and remain on post together.”

Officers were told to immediately report “any unusual conditions, especially the congregation of large groups. Please remind all uniform members of the service to remain vigilant on post, and to approach all situations tactically.”

Auxiliary patrols, made up of volunteers, have also been suspended, according to the letter.

The warning comes after a tense several weeks with the fatal shooting of police officers in Dallas, and fatal police-involved shootings of two men in Baton Rouge and Minnesota.