More details emerged Wednesday as Philadelphia police provided information on a deadly incident, in which officers chased and shot a boy after a shot was fired into the officers' car.

Police identified the boy as 12-year-old Thomas Siderio, and said in a statement he was shot in the back by an officer during a foot chase and he had a gun.

Immediately following the shooting in South Philadelphia on Tuesday night, police said they believed the boy who was shot was a teenager.

The shooting happened around 7:24 p.m. as four officers dressed in plain clothes were inside an unmarked car on a surveillance assignment related to a gun investigation, Philadelphia Police Deputy Commissioner Benjamin Naish said Wednesday during a virtual news briefing.

The officers saw two people on a street corner -- Siderio and a 17-year-old -- and observed one of them, the 17-year-old, was wanted for questioning in relation to the investigation. Officers drove toward the pair, officials said.

The officers activated the red and blue emergency lights on their unmarked car, and then heard gunfire and glass shattering from their rear passenger window, according to the statement.

At that point, two of the four officers immediately got out of the car and shot at Siderio as he ran, the statement said. Siderio "was still in possession of his firearm," according to the police statement.

One of those two officers continued to run after the boy and fired two more shots, "striking Siderio in the upper right back area one time, with the bullet exiting from the left chest area," the statement said. He was rushed to a nearby hospital and pronounced dead at 7:29 p.m.

Police said after the shooting a juvenile, who was not identified at the time, was killed after allegedly firing at the officers.

The initial police statement said the victim was the same person who fired at the officers.

But on Wednesday, during the news briefing, when asked, Naish did not definitively say Siderio fired the shot and noted the investigation is in its early stages.

"I can't be definitive about exactly everything at this point. But I can be definitive that a shot was fired into the police vehicle, and the gun was recovered," Naish said.

Police say they recovered the bullet inside the police vehicle.

The investigation remains ongoing.

A 9 mm semi-automatic handgun equipped with a laser was recovered from the scene, according to the police statement. The gun was reported stolen and was loaded with one round in the chamber and five rounds in the magazine.

When asked at the Wednesday briefing whether the officers gave verbal commands for the boy to drop his gun, the deputy commissioner responded, "I can tell you definitively that the police officers' vehicle had the red and blue lights indicative of police activity. I can't get into specifics about exactly what was or wasn't said. So, I'm just going to leave it that the police vehicle would, could be clearly identified based on the lights that this was a police vehicle."

Philadelphia officers in plain clothes do not wear bodycams, Naish said, noting investigators are working on gathering surveillance footage from the area.

The 17-year-old boy who was at the scene was not hurt, authorities said. He was questioned and released pending further investigation.

One of the officers was injured in the eye by glass when the car was shot and the bullet went through the passenger side rear window and then went through the headrest of the front passenger's seat where another officer sat, the police statement said.

The two officers who fired their weapons have been placed on administrative duty as the police department's officer-involved shooting investigations unit reviews the case, police Sgt. Eric Gripp said Tuesday.

Philadelphia Fraternal Order of Police Lodge 5 had no comment.

Jane Roh, communications director for District Attorney Larry Krasner, told CNN on Thursday that officer-involved shootings are investigated by police and the DA's special investigations unit. "This is an active and ongoing investigation and as such we have no additional comment at this time," Roh said.

And the office of Mayor Jim Kenney said it was investigating the circumstances of the incident.

"No matter what the outcome of the investigation is, this is a deeply troubling incident with a tragic loss of life," said spokesman Kevin Lessard. "The Philadelphia Police Department will conduct a fair and thorough investigation into this incident."

CNN reached out to the Philadelphia Medical Examiner's Office for more information. (CNN: Excludes headline)

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