A rookie NYPD officer “accidentally” shot and killed an unarmed African-American man in a staircase in a New York apartment block. It happened as Ferguson is tensely waiting for a grand jury decision on a police officer who shot Michael Brown.

Akai Gurley, 28, and his girlfriend Melissa Butler were entering a staircase on the seventh floor in Pink House project in Brooklyn late Thursday evening when two policemen came down from the eighth floor. Peter Liang and his partner, Shaun Landau were doing a top-to-bottom patrol. Liang, a rookie on probationary assignment, fired a shot in Gurley’s chest without a warning, Butler said.

“They didn’t present themselves or nothing and shot him,” Butler told DNAinfo New York. “As soon as he came in, the police opened the [door to the] eighth-floor staircase. They didn’t identify themselves at all. They just shot.”

Gurley and Butler tried to go down the stairs but reached only the fifth floor where Gurley lost consciousness. There a neighbor called an ambulance. Butler says the policemen did not come to help nor called the ambulance. Gurley, who has a 2-year-old son, was pronounced dead on arrival to hospital.

An NYPD spokesperson said the police department's internal affairs bureau is investigating the shooting. Liang has been placed on modified assignment and was relieved of both his badge and gun.

The police are collecting information from witnesses and radio reports without talking to Liang as according to the policy, he will be interrogated in the District Attorney’s office first and then by internal affairs officers.

"What happened last night was a very unfortunate tragedy,'' police commissioner Bill Bratton said in a statement. "The deceased is totally innocent. He just happened to be in the hallway. He was not engaged in any criminal activity.''

Bratton said it probably was an accidental discharge of weapon.

“So here’s an unarmed, black 28 year old in the stairwell,” former City Councilmember Charles Barron said as quoted by CBS New York. “Two officers, one Asian, one white, fully armed. He’s unarmed, they meet on the stairwell and he winds up dead with a bullet in his chest. I want to hear the justification for this one. Don’t tell me the hallway was dimly lit. That’s no reason to kill a black man on a stairwell.”

The incident happened while a grand jury decision concerning Michael Brown’s death is awaited. Unarmed 18-year-old Michael Brown was shot and killed in Ferguson by police officer Darren Wilson in August. The shooting caused riots in the area and tensions between police and the African-American community.