The fatal police shooting of an unarmed man in Brooklyn Thursday night appears to have been an "unfortunate tragedy," New York City Police Commissioner William Bratton said Friday.

The victim, Akai Gurley, 28, had spent the evening at his girlfriends apartment inside the Louis Pink housing projects, Bratton told reporters at a press conference. The couple left the seventh floor apartment around 11:15 p.m. and tried to take an elevator down to the bottom floor. When the elevator wouldnt work, they entered the stairwell.

Two officers, meanwhile, were conducting a vertical patrol -- also known as a top to bottom patrol -- inside the building. Upon entering the "dark" stairwell on the eighth floor, Bratton said, Officer Peter Liang drew his gun and flashlight as a safety precaution. That's when Gurley and his girlfriend -- identified by the New York Daily News as Melissa Butler -- also entered the stairwell.

At that moment, Liang fired one round from the eighth floor landing. Gurley, who was on the seventh floor landing, was struck in the chest.

Gurley and Butler then ran down the stairs before Gurley collapsed on the fifth floor. Under instructions from a 911 operator, Butler then tried to administer first aid. Gurley was transported to Brookdale Hospital, where he was pronounced dead on arrival.

Bratton said that according to a preliminary investigation, "it appears this may have been an accidental discharge." Gurley "was not engaged in any criminal activity of any type," Bratton said.

Akai Gurley was unarmed when he was fatally shot.

He didnt do nothing wrong," Butler said of Gurley, per the New York Daily News . "He was just standing there and they shot him. He was an innocent man.

Liang, Bratton said, has been on the force less than 18 months and was on probationary assignment to the housing bureau. Liang and the other officer were taken to the hospital to be treated for tinnitus, which is a ringing noise inside the ears, often caused by gunfire.

Bratton said he talked Friday morning to Brooklyn District Attorney Ken Thompson, who's investigating the incident. NYPD Internal Affairs is also investigating.

News of Gurley's death comes as the country awaits the decision of a grand jury in Ferguson, Missouri . The jury is expected to decide Friday whether officer Darren Wilson should be charged in the shooting death of unarmed, 18-year-old Michael Brown over the summer.

And in Staten Island, another grand jury is currently looking at evidence to determine whether NYPD officer Daniel Pantaleo should face charges for putting Eric Garner into a chokehold during an arrest for selling untaxed cigarettes. The maneuver, which is banned under NYPD guidelines, contributed to Garner's death.

New York City Mayor Bill de Blasio told reporters Friday, according to Capital New York , that the shooting of Gurley "does appear to have been an accident" and that people shouldn't "connect all the dots" between Gurley, Brown and Garner.

Other lawmakers on Friday expressed alarm and concern over Gurley's death.

"The senseless killing of another unarmed African-American male by the NYPD should shock the conscience of all New Yorkers and the nation," U.S. Rep. Hakeem Jeffries (D-Brooklyn) said in a statement. "At this point, talk is cheap. The community demands action."

"Our Mayor and the Police Commissioner must commit to a systematic change in the law enforcement culture of this City," he added. "Anything less will not be tolerated."

New York City Public Advocate Letitia James said she was "deeply disturbed" by Gurley's death.

The shooting of this unarmed man raises serious concerns about training and patrols in our citys public housing developments," she said in a statement.

Donna Lieberman, executive director of the New York Civil Liberties Union, expressed similar concerns.

"Given the long-standing concerns about vertical patrols and the mistreatment of public housing residents, this tragic shooting requires a close examination of vertical patrol tactics and training," she said in a statement to HuffPost.

Gurley's death recalls other fatal, police-involved shootings of unarmed black men in or near Brooklyn housing projects over the years.

Unarmed 19-year-old Timothy Stansbury was shot and killed by a police officer on the roof of a Bedford-Stuyvesant housing project in 2004. In 1994, unarmed 13-year-old Nicholas Heyward Jr. was shot and killed by a police officer inside the Gowanus housing projects after an officer mistook his toy gun for an actual weapon. And on Thanksgiving Day in 1976, an officer shot and killed unarmed 15-year-old Randolph Evans outside a housing project in Cypress Hills.

Bratton on Friday said that vertical patrols are an "essential part of policing" the city's housing projects. He said crimes can take place inside the buildings' stairwells and on the roofs.

"People in those developments want us there," he added, pointing to a recent spate of crime in the Louis Pink housing projects -- where Gurley was killed -- including a recent homicide.

This story has been updated with new information throughout.