One night last fall, in Newark, New Jersey, a young black man was walking home down a sidewalk on a residential street when he was approached by an officer from the city police department’s gang task force unit, whose priorities include getting guns off Newark’s streets.

“Don’t touch me, brother,” the young man calmly said to the officer. “Don’t even touch me.”

The young man was thin, dressed in slim-fitting jeans, a leather jacket, and a backwards hat. There was nothing immediately suspicious about this behavior. The officer shined a flashlight in his face. The young man paused and repeated his request: “Please don’t touch me.”

The officer grabbed him by the neck.

The man, now terrified, resisted for a moment, pleading with the officer to “hold up,” prompting several more policemen to descend upon him. Together, they took the man to the ground as he screamed, “I’m not doing nothing.” He was handcuffed, searched, and eventually released. He had no weapons or contraband in his possession.

The scene comes from the new “Frontline” documentary “Policing the Police,” directed by James Jacoby and produced by Anya Bourg, which debuts on June 28 on PBS. The film gains deep access to the embattled Newark Police Department, one of the most poorly functioning forces in the country. In 2014, after conducting an investigation, the Department of Justice released a scathing report showing that 80 percent of the people stopped by Newark police were black (compared with a little more than half of the city’s population), and that 75 percent of the police department’s stops lacked clear probable cause. The government also singled out the Newark police for a pattern of excessive force.

The Newark police department’s approach to law enforcement has not been successful; violent crime remains high. In 2015, there were 300 shootings in the city, and 109 murders, a rate nine times higher than that of New York City. As part of a settlement, the DoJ has required the Newark police department to undergo a series of changes, including retraining officers to become proficient in de-escalation techniques.

New Yorker staff writer Jelani Cobb serves as the film’s narrator and its primary reporter. One of the specific subjects he explores in “Policing the Police” is the relationship between gun violence and police brutality. As the film shows, decades of harassment and abuse have driven a massive wedge between officers and the people they serve. Members of the community see little benefit in cooperating with law enforcement; without the help of the community, it is all but impossible for law enforcement to effectively address violent crime.

Cobb went into the project wondering about the prospects for a law enforcement reboot in a place where crime and poverty are endemic. “I wanted to know how reform could happen in Newark,” he says. The film’s implicit answer is that a problem decades in the making has no quick solutions.

How are officers in the Newark police department dealing with all the scrutiny they’re currently facing?

On one hand, they think aggressive policing — used to get guns off the streets — is absolutely necessary. But it also makes people hostile toward them. And it’s not people involved in criminal activity who are hostile. It’s everyday people. Aggressive tactics makes it less likely for community people to cooperate with them. So there’s this cause and effect: People aren’t cooperating, so few homicides are solved. In Newark, I think the clearance rate is about 30 percent. That’s pretty bad.

What do cops themselves say about why the clearance rate is so low?

Some referenced the stop-snitching culture. Others said downsizing — the police force is down almost 25 percent since its peak size — has an affect on its ability to clear murders. Recruitment is also an issue. The starting salary of Newark police officer is not very high, and the force is competing with other area departments that have both a higher starting salary and less crime.

How do the police officers you encountered feel about guns?

I would hear officers say “guns kill.” It’s straightforward: In the grand pecking order of crime, they’re trying to stop murders in the city. So guns are the top priority, followed by intelligence and then drugs.

But the relationship between gun violence and bad policing is mutually reinforcing. When you have lawlessness, when there’s effectively no legal consequences for acts of violence, there will be more violence. Police think they have to respond forcefully to that violence, which causes more distrust between officers and the community people whose cooperation they need to solve crime. The cycle gives carte blanche to bad policing, and makes it less likely that the gun violence problem will get reigned in.

Newark is a city flush with weaponry, and people who have the illegal guns cops work hard to seize have them for the same reason as legal gun owners: because they’re afraid of crime.

How do officers decide who might be carrying an illegal gun?

I noticed that, with the police, there was a disturbing certainty in their instincts and suspicions. There would be this notion that, “Hey, this guy is up to something, and we have to stop him.” But was he really up to something? No, he was just walking down the street. The certainty in their instincts serves as a kind of of self-justification.

I interviewed one young man whose shoulder had been broken by police. He’s a 14-year-old boy who was walking to the store for his mother. Cops threw him down on the pavement during a stop-and-frisk. He didn’t even know they were police.

In the film, the gang task force really celebrates whenever it gets even a single gun off the streets. Do the Newark police really believe their tactics are paying off?

Over the course of a year, police take hundreds of guns off the street. It’s like garbage maintenance; the city has to take guns off the street, otherwise it will be overrun by them. So police would tell you they’re making the city safer and that aggressive force is necessary. They don’t see it as a violation. They also don’t have a clear perspective on how people could view their actions as wrong. It’s very difficult for them to imagine what it’s like to be on the other side of the interaction.

Did you ever feel sympathetic toward the officers you met?

Sure. When they’re out, and there’s a homicide, and they’re trying to investigate, trying to prevent a cycle of retribution and the community is being hostile toward them — that’s really tough. We interviewed an officer whose son was fatally shot. It was difficult for her to do her job because she sees people going through the same thing she went through. The worst moment of her life continually gets replayed in her mind.

[Photo: Spencer Platt/Getty Images]