SAN FRANCISCO (CBS SF) — A gun stolen from a San Francisco police officer personal vehicle was used days later in a gang-related killing, authorities said Wednesday.

The gun, a personal firearm registered to an unidentified officer, was stolen from his car on August 12, police said.

Three days later, on August 15, officers responded to reports of a shooting and found a 23-year-old man suffering from gunshot wounds.

The victim, identified as Abel Enrique Esquivel Jr., had been shot near the intersection of Cesar Chavez St. and Folsom Ave. as he walked home from work around 2 a.m.

Esquivel Jr. was taken to San Francisco General Hospital, but died from gunshot wounds to his abdomen and chest the next day.

Investigators determined the gun used in the homicide was the same one stolen from the officer’s car three day before.

Police arrested two suspects on Monday: 18-year-old Erick Garcia Pineda and 24-year-old Jesus Perez-Araujo, both San Francisco residents.

A third suspect was arrested Tuesday. Police identified him as Daniel Cruz, 18, also of San Francisco.

Pineda was booked of charges of murder, robbery, conspiracy, burglary and attempted murder; Cruz on murder, conspiracy, robbery and possession of stolen property; and Perez-Araujo on robbery, burglary and conspiracy.

San Francisco police Chief Bill Scott said, “We have confirmed that the gun was used in the homicide. We do have a personnel investigation to determine the circumstances under which how that gun was stolen, how it was secured.”

Outside Wednesday night’s police commission meeting at City Hall, a commissioner commented on the incident.

“I was surprised,” said San Francisco Police Commissioner Petra DeJesus. “Given the fact that guns in officers’ cars have been in the news in the last 18 months and crime being committed by that. I was concerned and surprised that there wouldn’t be more care in leaving a gun in a car.”

Earlier on Wednesday, San Francisco Police Officer’s Association president Martin Halloran issued a statement saying the officer did not know his weapon had been stolen.

“There were no visible signs of the burglary, and the officer did not realize that the vehicle had been broken into, nor that the firearm had been stolen,” said Halloran.

“The officer, a highly-decorated veteran, is devastated. He is working with the department to fully comply with its investigation into this case.”

Last year, the state of California enacted a law requiring all individuals, including law enforcement, to lock all weapons in an unattended car in a trunk or a lock box attached to the frame.

The city of San Francisco has a similar policy.

How the weapon that killed Esquivel Jr. was stored is one of the questions Internal Affairs is asking.

“As far as our department policy, there is a department policy on storage of weapons in vehicles, it’s pretty clear,” said Chief Scott. “The weapon is supposed to be stored in a locked container that is affixed to the vehicle. So, I don’t have the details for that because the investigation is ongoing, but there is a policy for that.”

It was not immediately clear whether the gun used in the homicide had been recovered by police nor was it clear whether it was used in any other crimes.

The three men arrested in connection with Esquivel Jr.’s homicide are scheduled to be in court Thursday morning.