Glen Grays, a postal worker in Brooklyn, had his delivery route cut short on St. Patrick’s Day when he was handcuffed by four plainclothes police officers and placed in an unmarked car.

Cellphone video filmed by a bystander shows Grays in his U.S. Postal Service uniform, holding a package, when the officers approach him. The video doesn’t show what led up to the encounter.

The footage was released this week by Brooklyn Borough President Eric L. Adams, who said Grays had been “carrying out his normal duties” as a mail carrier when he got out of his truck and “a vehicle passed by him, almost striking him.”

“He made comments to the vehicle, as any New Yorker would,” Adams said at a news conference last week. “The occupants of the vehicle stopped, backed up when he was crossing the street delivering the package.”

According to Adams, those occupants were the four plainclothes officers, who followed Grays to his delivery stop. The video shows the officers telling Gray to “stop resisting.” They then take him away in handcuffs, leaving his mail truck unattended.

Yelling at the unmarked car about driving recklessly “is the only action that Glen did that day that caused those plainclothes officers to stop their vehicle and to show who’s the biggest and the baddest and place handcuffs on an on-duty postal employee who is delivering the U.S. mail,” Adams said. “If they would do that to Glen, in his postal uniform, they would do it to any other person of color in this community.”

Asked about the incident, the New York Police Department said only that “the matter is under internal review.”

Mayor Bill de Blasio “will be in close touch” with Police Commissioner Bill Bratton “about this incident’s investigation and findings,” Monica Klein, the mayor’s deputy press secretary, said in a statement.

“We expect all members of NYPD to act professionally and respectfully,” Klein said.

The National Association of Letter Carriers “is troubled by this incident,” president Fredric Rolando said in a statement to The Post on Monday. “We trust that the police department will investigate this matter thoroughly and expeditiously, and that any necessary actions will be taken.”

Grays, who said he was issued a summons for disorderly conduct that requires him to appear in court in May, told “CBS This Morning” on Monday that he “was extremely terrified” during the encounter. He said he has never been arrested nor received a summons before.

“The only thing that saved me, I think, is because I was on videotape,” Grays told CBS. “I was afraid if I didn’t comply, something was going to happen to me.”

Grays is engaged to a New York police officer he met while on his delivery route, the New York Times reported.

“I don’t hate cops,” Grays told the newspaper. Pointing to his fiancee, he said: “I’m marrying one.”

Adams said Grays did nothing wrong in the video, adding: “It’s hard not to believe that the only reason Glen was handcuffed is because [of] the color of his skin.”

Grays is African American.

“It’s sad,” Grays told CBS. “I thought that when I put on that uniform, that I would be treated a little different. But it’s no difference. I’m just another brother with a uniform.”

The NYPD has come under fire in the past for policies that critics said disproportionately targeted people of color.

Fatal encounters with New York City police have brought additional scrutiny to the department: In 2014, an unarmed black man, Eric Garner, died after he was taken to the ground by officers and put in what appeared to be a chokehold. The incident was caught on tape and ignited protests across the country, with Garner’s last words, “I can’t breathe,” becoming a rallying cry.

That same year, a rookie officer fatally shot Akai Gurley, an unarmed black man, in the stairwell of a Brooklyn housing project. The officer, Peter Liang, was convicted of manslaughter and fired from the department.

In 1999, an unarmed African immigrant, Amadou Diallo, was gunned down by four New York City police officers in front of his apartment building, in a hail of 41 bullets.

Sonya Sapp, the mother of Glen Grays, said this week that she cried when she watched the video of her son’s arrest. He is the eldest of her six sons.

“I worry about all my boys, every minute, every second of every day,” Sapp said at a news conference last week.

The video begins by showing plainclothes officers approaching Grays, who is holding a package. Not all of the words they exchange are clear.

“You want my ID? My ID is right there inside of the truck,” Grays tells the officers, pointing to the vehicle.

The officers tell him to get his ID. Grays is heard telling them that he is delivering mail on his postal route. Two officers pull him away from the door. The package, having fallen to the ground, is kicked away by an officer.

Grays is told to put his hands behind his back.

“Stop resisting,” officers tell him.

“He almost hit me,” Grays says. “I’m not resisting.”

“Put [your hands] behind your back, or you’re going to get f—— hurt,” one officer tells him.

Four officers surround Grays, who repeats, frustrated: “I’m not resisting.”

“Get off of me,” he says.

The four plainclothes officers eventually lead Grays, handcuffed, to their unmarked black car.

An officer frisks him and puts him in the car.

Bystanders yell at the officers throughout the encounter. Some recognize Grays and call out to him by name. The video ends there.

Adams, the borough president, said that after the police vehicle drove away, it rear-ended another car and that Grays, who wasn’t placed in a seat belt, was injured in the crash.

The driver, who had turned around to taunt him, hit the vehicle in front of them, Mr. Grays said, causing him to bang his shoulder against the front seat. Mr. Grays was then taken to the 71st Precinct station, where he was issued a summons for disorderly conduct that will require him to appear in court. He was then released.

In a televised interview with CBS on Monday, Grays said he wanted the officers involved to be disciplined, but “I don’t want them to be jobless. They might have families, kids they have to support.”

Adams denounced the actions of the officers, saying that he was deeply troubled by the treatment of a federal employee and that the “major steps” taken by de Blasio and Bratton to reform police practices haven’t gotten “down to the street.”

“This could have been another Eric Garner situation if Glen had not responded as calmly as he did,” Adams said.

[This story, originally published March 25, has been updated.]