Officer Dorian Young, a 24-year veteran assigned to the 15th District, has been placed on restricted duty as the investigation continues into the Sept. 5 incident.
According to a police department statement released Friday, Young "discharged his .40 caliber semi-automatic pistol two times, striking his son in the abdomen/back. Philadelphia Fire Department Medic #17 transported the shooting victim to Aria Hospital, where he is listed in critical condition."
The incident happened at 6:30 p.m. Monday at the officer's home in the 2700 block of Taunton Street.
Police say four people were inside the home, including Young, who was off-duty at the time.
They say the officer got into an argument with his son, which escalated into a physical altercation.
During the altercation, police say, the officer's personal gun was fired twice, striking the 19-year-old man both times.
"Apparently they got into a scuffle, argument or something," Police Commissioner Richard Ross told Action News the day after the shooting. "The officer accidentally or inadvertently discharged his weapon. We're still trying to figure out if it was intentional or not."
The two other people in the home at the time, a much younger son and the gunshot victim's girlfriend, were questioned.
People on the block were surprised by the violence, especially at the home of a police officer they know to be a good neighbor.
"Shocked because the dad is usually a laid back guy. For him to pull something like that it would have had to be really bad. How do you respond to something like that? Nobody wants to shoot their own son," Roseanne Mauro of Northeast Philadelphia said.
The officer would have been placed on administrative duty, but he was already on medical leave after suffering an injury on the job.
The DA has yet to decide whether criminal charges are warranted. Once that's decided, Internal Affairs will recommend whether he should keep his job.