Berkeley police have suspended an investigation into an off-duty San Francisco police officer who shot at another driver he thought was pointing a weapon at him last fall, following detectives’ unsuccessful attempts to locate the driver of the second car.

Officer Michael Shavers, who joined the San Francisco Police Department in 2006, was driving to pick up his children from school when he used his department-issued weapon to shoot at a driver who allegedly overtook him at a Berkeley intersection on Sept. 13.

Shavers, who did not report the shooting to Berkeley police for more than an hour, said the other driver made a threatening motion by extending a hand out of a driver’s side window with what the officer believed to be a gun.

Berkeley police investigated the shooting but never found the car Shavers shot at or the other driver, despite sifting through surveillance video and distributing photos of the suspected car to neighboring law enforcement agencies. Detectives were unable to determine whether the other driver was injured.

Jennifer Wilson, a police sergeant who investigated the shooting, told The Chronicle that authorities would probe any new information if it becomes available.

“The case should really be considered ‘suspended’ pending further information from the other involved party,” Wilson said. “That person has not yet been identified, nor is there information on the license plate of that car.”

Teresa Drenick, a spokeswoman for the Alameda County district attorney’s office, said the case was never presented to prosecutors for consideration of charges.

The shooting was first reported by the San Francisco Examiner.

San Francisco police policy requires officers to remain at the scene of a shooting outside of the city and call local authorities, as well as immediately contact the on-duty supervisor of their unit or detail. Shavers told investigators he called his wife, lawyer and union officials before calling Berkeley police.

Shavers was reassigned from the San Francisco Police Department’s field operations bureau to special operations while officials conducted an administrative investigation, said Officer Adam Lobsinger, a department spokesman.

Don Nobles, Shavers’ lawyer, declined comment when reached by phone, saying he could not discuss an ongoing investigation.

Shavers told investigators he was on his way to pick up his children from school after an overtime shift when the driver of a silver Honda Civic tried to pass his Cadillac Escalade, according to a Berkeley police report obtained through a public records request.

The driver of the Civic eventually passed Shavers before stopping at the intersection of Eastshore Highway and Hearst Avenue.

Shavers told detectives he rolled up next to the Civic, uncertain if the driver was having a medical emergency. His passenger-side window was open, Shavers said, as was the Civic’s driver-side window.

“What’s up, man?” said Shavers, who lifted his hands and was in plain clothes.

Meanwhile, the cars remained about 5 feet apart.

It looked like the driver of the Civic was trying to reach for something, Shavers told Berkeley police, so he stretched his arm back and unholstered his department-issued .40 caliber handgun from his duty belt, which was on the floor behind his car’s center console.

“At that point, that’s when he came out his window with his arm extended towards my car,” Shavers said, “and I saw light reflect off something.”

Shavers pointed his gun through the passenger-side window and fired a single round. Detectives believe the incident occurred at 3:42 p.m.

The driver appeared startled and sped off, said Shavers, who apparently followed in an attempt to get the driver’s license plate. He eventually drove to El Cerrito, pulled over near his son’s school and tried calling his San Francisco police union representative to no avail. When he drove to his son’s school, his representative called him back. Shavers then called his wife before Tony Montoya, the union president, called him.

Montoya directed Shavers to call Berkeley police and return to the scene immediately.

Shavers called Berkeley police’s non-emergency line at 4:53 p.m. and identified himself as an off-duty officer who had been in an officer-involved shooting. Montoya had called police approximately 12 minutes before to report an off-duty officer had been involved in a shooting.

When a sergeant later asked Shavers if there was a reason why he didn’t just drive away when the driver appeared to be reaching for something, Shavers replied that he did not know.

“I don’t have an answer for that,” he said. “I don’t know, I think I was just transfixed on what was happening and then, you know, ’cause all this happened within a matter of like, seconds, I’d say 10 seconds max, so yeah, I don’t have an answer for that.”

Officials obtained video surveillance and distributed a bulletin to neighboring law enforcement agencies with two photos of the Civic and a brief description in hopes of identifying the driver and the car.

Wilson asked Shavers during an interview if the driver of the Civic committed an assault.

“Yes, based on, you know, the ... him coming out the window and pointing something at me,” Shavers said. “If it was a gun or something else, I don’t know what it was but I remembered seeing something in his arm extended towards me, made me feel like I was under attack and that’s why I returned fire in defense of my life.”

Alejandro Serrano is a San Francisco Chronicle staff writer. Email: alejandro.serrano@sfchronicle.com Twitter: @serrano_alej