NEW YORK (Reuters) - As Akai Gurley bled to death in a New York stairwell, the police officer who fired the fatal bullet was upstairs arguing with his partner about whether to call in the incident, prosecutors said at the start of the officer’s trial on Monday.

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New York Police Department Officer Peter Liang is charged with manslaughter and other crimes in the Nov. 20, 2014, shooting inside a Brooklyn public housing project.

“Akai Gurley is dead today because he crossed paths with Peter Liang,” Brooklyn Assistant District Attorney Marc Fliedner told jurors in his opening statement.

Defense lawyer Rae Koshetz said Liang fired his gun accidentally and that he had no idea the bullet had ricocheted off a wall into Gurley’s chest in the “pitch-black” stairwell.

“This was a million-to-one possibility,” she said.

The death of the 28-year-old Gurley, an unarmed black man, added to nationwide tensions over police use of force against minorities. Liang, 28, is Chinese-American.

Just days after the incident, a grand jury declined to indict a white police officer for killing black teenager Michael Brown in Ferguson, Missouri. Less than two weeks later, a New York grand jury cleared a white officer in the chokehold death of Eric Garner.

Koshetz told jurors the case was “not a referendum on policing in the United States.” The 12-member jury is almost entirely white.

Liang drew his weapon as he and his partner, Shaun Landau, entered the stairwell on patrol late at night. Gurley and a friend were walking one floor below on their way out of the building.

Prosecutors have not accused Liang of intending to shoot anyone. But they said he acted recklessly in unholstering his weapon and then failing to check whether the bullet hit anyone because he was too worried about losing his job.

Liang also did not administer first aid, prosecutors said.

But Koshetz said Liang was in a “state of shock” following the shooting, eventually requiring his own ambulance, and was in no condition to help anyone. Drawing his gun inside a dark, “crime-ridden” housing project was not against department rules, she said.

The trial’s first witness, building resident Melissa Lopez, described relaying instructions from a dispatcher to Gurley’s friend, who was desperately trying to revive him.

“He’s not breathing!” the friend, Melissa Butler, screamed during a recording of the 911 tape played in court.

Lopez said Liang stood by “doing nothing the whole time.”