A relative of a man who was fatally shot by D.C. police as he drove away from officers, who had found him unresponsive in a running car with a gun tucked in his waistband, is demanding to know what prompted a sergeant to fire 10 times at the vehicle.

“I want to know, ‘How did we get to the point he was a threat?’ ” said LaShunna Grier, the cousin of the man killed, 27-year-old An’Twan Gilmore, who was shot in the early-morning hours of Aug. 25 at New York and Florida avenues NE.

It also is the central question police investigators are trying to answer as they sift through evidence and talk to witnesses.

Police have said they did not know precisely what happened inside the car when Gilmore stirred as police knocked on the car window, or why Sgt. Enis Jev­ric fired. Jevric, who has been on the force nearly 14 years, did not give a statement to detectives, as is his right while prosecutors review the shooting. He has declined to comment.

Police said Gilmore’s loaded handgun was in his waistband when police first saw him unresponsive in the driver’s seat. They said the gun was in the same place when he was found in the vehicle after the shooting.

Police have said video of the crucial moments leading up to the shooting from Jevric’s body camera was obscured by a ballistic shield he was carrying as he approached the vehicle. It is not clear what other officers saw. Jevric was the only officer of about six at the scene who fired a gun.

Police Chief Robert J. Contee III told reporters last week that “firing at a moving vehicle is inconsistent with our policies,” and he said that aspect of the case is also under review. He asked the same question as Grier about Jevric’s decision to fire: “What did he perceive to be the threat at that point?”

The chief said the shooting was referred to the U.S. attorney’s office in the District.

The incident began when police received a complaint about a blue BMW stopped in a travel lane, at an intersection, and the driver appeared to be sleeping.

A police officer was dispatched at 2:47 a.m. A Basic Life Support ambulance was sent about 26 seconds later. At 2:55 a.m., an officer called for additional help because “the person is armed in the vehicle,” according to a summary provided by the District’s 911 center. The ambulance arrived at 2:59 a.m.

Grier has questioned why her cousin did not get immediate medical attention. She said Gilmore had medical issues that caused seizures but that he did not have a specific diagnosis.

Authorities and official reports have alternatively described Gilmore as unresponsive, asleep or unconscious. Police have said they don’t yet know Gilmore’s condition before he was shot.

Police would not comment on specifics but said it is procedure to render a scene safe, such as removing a firearm, before letting in medical personnel. Video from a bystander captured an ambulance parked across the street, its lights flashing, as police surrounded Gilmore’s vehicle.

After officers arrived, police said, they regrouped for about 20 minutes to plan how to approach the vehicle. Gilmore had his left foot on the brake, police said. Video from body-worn cameras shows officers gathered around the car and, at one point, an officer tapped on a window.

That apparently woke Gilmore, who lurched forward in the vehicle and then stopped as police yelled, the videos show. Gilmore then drove away as Jevric fired. The shots came in two distinct bursts, with several fired as the car headed away from the officers. The vehicle crashed a few blocks away, and police said the gun Gilmore had was a Glock handgun loaded with 17 bullets.

The ambulance crew that had responded earlier went to assist Gilmore, and a separate paramedic unit also was dispatched, according to city officials. He was taken to a hospital, where he died.

Grier said Gilmore grew up in the Park Morton area of Northwest Washington and lived most recently in Shaw. His mother died when he was 8 years old, and his godmother, who helped raise him, also has died. Grier said he had two sisters and worked in construction.

In the days after the shooting, demonstrators gathered at the shooting scene and marched to the 5th District station, where Jevric is assigned. They have raised questions about the way officers approached the vehicle and why one of them shot his gun.

Philip M. Stinson, a criminal justice professor who studies police conduct at Bowling Green State University in Ohio, said the case could come down to what Jevric saw inside the vehicle and whether he or others faced an imminent threat.

“I think that the investigation is going to focus on exactly what the officer saw,” said Stinson, who reviewed police reports and the body-camera video from the incident. “The other officers apparently did not perceive such a threat and exercised appropriate and professional restraint in not firing.”

But, Stinson said, “that does not mean [the sergeant’s] actions were unjustified.”

Lois James, an assistant dean for research at Washington State University College of Nursing, where she studies stress and performance in high-stress jobs, including law enforcement, agreed that the investigation may hinge on what the sergeant saw Gilmore doing with his hands. Police officers are legally justified to use deadly force if they reasonably believe their life or the lives of others are in imminent danger.

James, who is also an adviser to the International Association of Chiefs of Police and reviewed the body-camera video in this shooting, said Gilmore was “clearly impaired behind the wheel,” though the reason is not clear. She asked: If police had time to retrieve a ballistic shield — which she called a sound tactical decision — why didn’t they block the BMW to prevent it from being driven away? Police did not respond to questions regarding tactics.

James said officers had to be concerned about an impaired driver leaving the scene, and the firearm. She said the positioning of the driver — his foot on the brake of a running vehicle at a stop light — shows that “it was not a conscious choice of the driver. This driver had not pulled over and taken a nap.”

At the time he was shot, Gilmore was being sought on an arrest warrant for an assault with a dangerous weapon, though police said the officers who responded to the distress call did not know that at the time.

Grier said Gilmore’s sisters watched the police body-camera video at a viewing provided by the city before it became public. She said she couldn’t watch then but has seen parts of the videos now posted online by police.

“There are so many questions that need answering,” she said of watching the police shooting.

Grier said she didn’t know why Gilmore had a gun, though she surmised it might have been for protection. She said she believes he did not reach for the gun, noting police said it was in the same place after he was shot as before, and that he possibly became scared when he awoke to see officers.

“He probably was very startled,” Grier said, which prompted him to drive off.

She described her cousin — whose name was initially misspelled as Antwan by police — as a practical joker who loved sports and helping his younger relatives at play. He had been planning to take a nephew to football practice the day after the shooting.

Grier said the family is upset with police who told reporters about Gilmore’s outstanding arrest warrant and that the car he was shot in was not his, saying it painted an unflattering portrait and detracted from the conduct of police.

Gilmore’s sisters did not want to talk but issued a statement through Grier saying the family is “processing our grief at the loss of our beloved brother” and concentrating on a funeral.

“Moving forward,” the family said, “we look forward to ensuring justice is served and those responsible are held accountable.”