Gun stolen from San Francisco deputy’s truck outside Pinole gym

This is a file photo of a Glock 17 pistol like the one reportedly stolen from a San Francisco sheriff’s deputy in Pinole on June 14. This is a file photo of a Glock 17 pistol like the one reportedly stolen from a San Francisco sheriff’s deputy in Pinole on June 14. Photo: Image Courtesy TimoStudios Photo: Image Courtesy TimoStudios Image 1 of / 28 Caption Close Gun stolen from San Francisco deputy’s truck outside Pinole gym 1 / 28 Back to Gallery

A thief stole an off-duty San Francisco deputy sheriff’s personal firearm that had been left unsecured in his truck last week outside a gym in Pinole, officials said Wednesday.

Police have arrested a suspect, but the boosted 9mm Glock 17 semiautomatic pistol has not been recovered, authorities said. The suspect was not immediately identified, nor was the deputy.

The San Francisco Sheriff’s Department has opened an investigation into the matter, said Nancy Crowley, an agency spokeswoman.

“The sheriff considers this very concerning and immediately took steps to investigate,” Crowley said of Sheriff Vicki Hennessy.

The incident happened around 7:30 a.m. on June 14 when the deputy left his truck outside Anytime Fitness at 1477 Fitzgerald Drive in Pinole, officials said.

The thief broke into the vehicle and stole the gun and four ammunition magazines, all of which were inside a backpack under the backseat of the truck, Crowley said.

Police arrested the suspected thief the same day as the break-in but did not recover the gun or magazines, officials said. Pinole police officials did not immediately return phone calls Wednesday.

State law requires that anyone transporting a firearm in a vehicle must lock it in the trunk, or in a locked container separate from the vehicle’s glove compartment, if the vehicle does not have a trunk. A violation is an infraction punishable by a fine up to $1,000. Police officers carrying out official duties are exempted.

The theft was the latest in a series of incidents in which law enforcement officials have had firearms stolen after leaving them unsecured in vehicles. Some of the incidents have ended in tragedy.

A gun taken from a San Francisco police officer’s personal car, while it was parked in the city, was used in the killing of Abel Esquivel Jr. in the Mission District in September 2017, authorities said.

Antonio Ramos was shot in September 2015, while painting a mural in Oakland, by an attacker who used a gun stolen from a U.S. Immigration and Customs Enforcement agent’s rented car in San Francisco.

In July 2015, a gun stolen from a car belonging to a U.S. Bureau of Land Management ranger in San Francisco was used, just days later, in the high-profile killing of Kate Steinle on Pier 14.

The Chronicle reported that after the 2015 cases, some Bay Area police departments bought officers lockboxes that can be fastened to the interior of their vehicles, providing stronger security — but many others did not.

The San Francisco Board of Supervisors considered making it a misdemeanor — punishable by up to six months in jail — for off-duty officers to leave a gun unsecured in a car. But the board ultimately voted to exempt San Francisco officers and deputies and apply the measure to everyone else, as long as the police and sheriff’s departments enforced internal policies.

The civil grand jury in Marin County, in a report released in May 2016, said just one police agency there had toughened policies on gun storage in vehicles since Steinle’s death, and that most agencies did not use lockboxes.

Evan Sernoffsky is a San Francisco Chronicle staff writer. Email: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky