NEW YORK — The call came in just after dark Tuesday — a man with a gun was robbing a T-Mobile store in Queens. A bystander outside the store said two employees had been taken to the back of the store.

The response was instantaneous, according to a recording of police dispatch calls. Officers spoke over one another on their radios, announcing they were en route: “Show me going,” each said in rapid succession.

The dispatcher responded with the standard police directive to drive safely — “Arrive alive,” and added, “No sirens, guys.”

The first officers to arrive were in street clothes, officials said. They ran inside. More officers pulled up outside, and then still more.

Then everything went wrong.

The officers who had arrived outside, apparently unsure what had happened in the store, began firing."Multiple officers fired multiple rounds,” Commissioner James P. O’Neill said at the hospital Tuesday night.

When it ended, the men who had run out of store lay bleeding on the ground.

Neither was the robber. They were brother officers, struck by friendly fire. One of them, a veteran detective, died from his wounds. A sergeant was struck nearby — “I’m shot,” he said into his radio. “Perp’s still in location.”

The man in the store was quickly caught. In a final, terrible twist to the tragedy, the gun he had carried turned out to be fake, police said. Lethal in appearance, but harmless.

One person briefed on aspects of the investigation said that at least three dozen shots were fired. More than 18 hours after the shooting, the Police Department had yet to publicly disclose how many officers had opened fire.

The person briefed on the investigation said he was told in the initial hours after the shooting that at least four officers had fired their weapons, but that he has since heard that number may be higher.

Those seconds of blind confusion will be parsed in the days and weeks ahead, as police seek to learn how such a chain of events could occur and how a recurrence could someday be prevented.

Detective Brian Simonsen, 42, a 19-year veteran, was fatally shot in the chest, the police commissioner said. He was the first New York City police officer to be killed in the line of duty since July 2017.

“It’s a very difficult and painful night for our city,” Mayor Bill de Blasio said at Jamaica Hospital Medical Center on Tuesday night. “We lost a very good man.”

The sergeant who was struck, Matthew Gorman, 34, underwent surgery for a gunshot wound to his thigh and was expected to recover. The robbery suspect was identified as Christopher Ransom, 27, of Brooklyn, a man with a history of prior arrests for minor crimes whom police were looking for in connection with another robbery of a cellphone store in January. He was shot eight times, police said, but details of his injuries were not immediately disclosed.

Details of fatal police shootings in New York can be slow to emerge in the initial 24 hours, in part because police investigators do not typically interview the officers who fired shots for reasons related to the Fifth Amendment. Instead, investigators begin by gathering the accounts of officers who were present but did not open fire.

The specific circumstances surrounding Simonsen’s shooting remained unclear Wednesday morning. His appearance in his Police Department portrait — white, stocky and bald — was in stark contrast to the description the police had of the robber, a black man. The detective was dressed in civilian clothing, police said. He was shot in the chest, police said, suggesting he was not wearing a vest, although those details were still unclear Wednesday morning.

The span of time from the initial call of a robber in the store to the gunfire was less than three minutes, playing out in a harrowing recording of the radio calls, captured by the Broadcastify website. “Shots fired! Shots fired!” an officer shouts, his voice cracking. Dozens of gunshots ring out in the background.

Almost immediately after came calls to send an ambulance for an “MOS,” member of service. Simonsen was taken to Jamaica Hospital Medical Center in a squad car. “His fellow officers put him in a marked police car and transported him here, where the trauma staff did their best to try to save him,” O’Neill said. “We thank them for that. They were unable to do so, however.”

A passing civilian drove Gorman to the same hospital.

This article originally appeared in The New York Times.