A New York City police officer shot and killed a “totally innocent” man in what law enforcement officials believe was a tragic accident, the city’s police commissioner said Friday

The incident occurred late Thursday as unarmed 28-year-old Akai Gurley was leaving a building in Brooklyn close to where rookie officer Peter Liang was patrolling.

The 27-year-old officer, with just 18 months on the force, had drawn his weapon while conducting a “vertical patrol” of an eight-story public housing complex in East New York, a mostly black section of Brooklyn that suffers from high rates of poverty and crime.

Gurley’s death comes amid a national debate over the use of police force in the light of the death of unarmed black teen Michael Brown in Ferguson in August. Gurley was also black.

But it also shines a light on the practice of sending rookies out to often-dangerous parts of town without a more senior police officer accompanying.

Recent assaults and robberies in the neighborhood had brought the NYPD to assign more officers to East New York, Police Commissioner Bill Bratton told reporters Friday.

“What happened last night was a very unfortunate tragedy,” said Bratton. “It appears that this may have in fact been an accidental discharge.”

The commissioner added that radio communications made by the officers at the time appear to corroborate the story of an accidental discharge.

Bratton went on to describe how officer Liang and his partner, also relatively new to the 50,000 strong New York City police force, ascended a building in the Louis Pink housing project and then made their way down the stairwell.

Seeing that the stairwell's eighth floor landing light was out and the way "pitch black," Liang decided to draw his weapon, alongside his flashlight, and make his way down to the seventh floor, Bratton said. Just as he did, Gurley and his girlfriend, Melissa Butler, opened a door onto the seventh floor landing.

Liang, about 12 feet away, fired his gun once, striking Gurley in the chest. The shot man, a father to a 2-year-old daughter, continued down the stairs to the fifth floor, bleeding, where he collapsed.

“The cop didn’t present himself, he just shot him in the chest,” a distraught, tearful Butler told The New York Times.

Butler stayed with her boyfriend until the two rookie cops, continuing down the stairs, reached them moments later. Neighbors and the officers called for an ambulance. Doctors at Brookedale hospital pronounced Gurley dead at about 11:55 p.m.

Bratton said that an investigation into the fatal shooting is underway and that the police department will review its methods of conducting patrols of housing projects. Soon, Bratton said, the rising class of police recruits will have more supervision from more experienced officers.

A representative of the police union said stairwells present a “dangerous and highly volatile,” environment that, along with illegal guns, threaten officers.

“The Pink Houses are among the most dangerous projects in the city and their stairwells are the most dangerous places in the projects,” read a statement from Patrick J. Lynch, of the Patrolmen’s Benevolent Association. “Only time and a thorough investigation will tell us what transpired in this case.”

But for Vince Warren, executive director of the Center for Constitutional Rights, which has lobbied the courts for police reform, the takeaway from this case is clear: “This is part of a national problem that has become a local tragedy,” Warren said. “The national problem is that police are policing entire communities instead of policing crime.”

Warren’s group successfully fought in federal court for the end of “stop-and-frisk,” a practice that saw police stopping and searching minority New Yorkers far more than whites and which was deemed racially biased.

Warren said that “the police, the police union, community groups, civil rights organizations, and religious groups” should come together to figure out how to keep streets safe without police endangering the lives of unarmed citizens walking them.

But this might not be so easy, argues Joe Giacalone, a former NYPD sergeant who served from 1992 until 2012. Giacalone’s career spanned the years of high crime in the early 90s, when the city saw over 2,000 murders a year, to the end of former New York City mayor Michael Bloomberg, when murders fell by about 75 percent.

Those years saw both an expansion of the city’s police force in terms of numbers, but also more “proactive” policing tactics. Giacalone said communities demand police stop crime, but they don’t back them up when a tragedy like Thursday night’s happens.

“You’re going to see mistakes made,” with proactive policing tactics, he said, lamenting a lack of cooperation from communities in high-crime areas. “You’re going to see more complaints and questioning about police tactics when there are few crimes, but the reason there’s little crime is because of these proactive tactics.”

For those who question why Liang had his gun drawn at all, Giacalone said it's hard to second-guess a police officer who might be in fear for his or her life.

“The community doesn’t really know what it wants. And, listen, I’ve never seen such an anti-police bias in this country. It seems they are whipping boys and girls for the problems in every community.”

But Warren says cities shouldn’t chalk up the occasional accidental death at the hands of the police as the cost of low crime rates.

“When tragedy strikes, the police department says it’s a terrible mistake and they’re sorry,” he said. “That’s not good enough.”