A Chicago police officer fatally shot a 24-year-old black man who authorities said pulled a gun while running away, prompting questions from the man’s family about why the encounter turned deadly.

Sgt. Rocco Alioto said the “armed confrontation” Wednesday evening on the city’s South Side happened as officers conducted a narcotics investigation. He said the suspect fled on foot when officers approached. Alioto said in a statement that officers told the man to stop and he “produced a weapon,” so the officer shot him.

The man, later identified as Maurice Granton Jr., died of a gunshot wound to the back, the Cook County Medical Examiner’s office said Thursday. The Civilian Office of Police Accountability, which is investigating the shooting, said late Thursday that preliminary evidence shows there were three shots discharged from the officer’s firearm.

Police spokesman Anthony Guglielmi said that officers involved in a narcotics investigation were watching the area Wednesday evening through one of a number of surveillance cameras mounted on poles throughout the city. They saw Granton taking part in what appeared to be an illegal drug transaction and dispatched officers to the scene.

Guglielmi posted on Twitter a photograph of what he said was Granton’s weapon found at the scene. He said that there is physical evidence that the gun had been fired. No officer was shot although a sergeant may have suffered a broken ankle during the confrontation.

The police department has not released the name or race of the officer involved in Wednesday night’s shooting. Alioto said the officer has been placed on 30-day administrative leave in line with department policy.

The shooting of Granton comes as police have faced intense scrutiny over allegations of excessive force involving black suspects. White officer Jason Van Dyke has been charged with first-degree murder in the 2014 shooting of black teenager Laquan McDonald. He has pleaded not guilty. Release of a video of the shooting of McDonald a year after it happened prompted outrage and calls for Mayor Rahm Emanuel to resign.

Chicago police released more details of the Wednesday shooting after Granton’s sister, Joanna Varnado, suggested that the officer had used excessive force.

“Since when does running validate somebody getting shot?” she asked. The Chicago Tribune reported that Granton’s family expressed doubts that the gun belonged to Granton, the father of two young daughters.

“I just want to know what the real story is,” Varnado said. “If it was misconduct, I want justice. My brother was 24 years old. He loved his girls. That’s all he lived for, was his kids.”

(AP)