An NYPD cop was shot and wounded during a wild subway shooting in Brooklyn Sunday afternoon that also left three others injured — all seemingly hit by police bullets, authorities said.

Cops said the bloody encounter in Brownsville started shortly after 3 p.m. when cops confronted a farebeater at the L line station on Sutter Avenue, NYPD Chief of Department Jeffrey Maddrey said at a press briefing.

The man, identified by law enforcement sources as 37-year-old Derrell Mickles, refused to stop and muttered, “I’m going to kill you if you don’t stop following me,” the chief told reporters.

“The male turns around and confronts the officers,” Maddrey said. “They become aware that he has a knife in his pocket. They give numerous commands. The male basically challenges the officers.”

Mickles then allegedly hopped onto a train when it pulled into the station, with both officers then deploying their Tasers — which failed to stop him.

He then lunged at one of the cops with the knife, the chief said.

“The officer stands back, he draws his weapon, and then both officers at this point fire,” Maddrey said. “They fire multiple rounds and the male goes down and they’re able to handcuff him and subdue him.

“While they’re subduing him one of the officers realizes that he’s hit as well,” the chief said, adding that the cops realized that the suspect was wounded while searching him — and later realized that two bystanders near the scene “were both struck by gunfire” as well.

All of the injuries appeared to be caused by police fire.

“I don’t like to use [the] term ‘friendly fire,” but absolutely we believe at this time that our officers were the only ones who discharged weapons…everyone that was struck this afternoon we believe was by our officers,” Maddrey said.

The wounded officer, who was struck in the shoulder, was transported to Brookdale Hospital with non-life-threatening injuries, the sources said.

Other victims were taken to Brookdale and Kings County Hospital.

“In my 30 years of law enforcement I’ve learned that policing is a very, very difficult job,” interim NYPD Commissioner Thomas Donlon said.

“Make no mistake,” he added, “the events that occurred on the Sutter Avenue Station platform were the result of an armed perpetrator. He was confronted by officers doing the job we asked them to do.”

According to sources Mickles has 20 prior arrests, most on burglary charges dating to 2003, and is currently suspected in two other heists.

The shooting investigation forced authorities to shut down the Sutter Avenue L line at the Broadway junction.

Law enforcement sources previously believed two cops had been struck.

Additional reporting by Valentina Jaramillo and Larry Celona.