A man sought by police allegedly stole a San Francisco police car in the Marina district Saturday morning, leading officers on a long chase throughout the city that ended with shots being fired on Treasure Island.

While police chases are somewhat common, ones involving stolen police cars are not.

“Throughout my career it has happened maybe once before, and I have been in law enforcement for 27 years now,” Deputy Chief Hector Sainez said at a news conference Saturday afternoon.

The incident began at 8:15 a.m., when San Francisco police responded to reports of a man with a knife at Chestnut and Lyon streets. But when an officer approached the suspect, whose identity has not been released, the man reportedly jumped into the police car, used the keys still in the vehicle’s ignition, and took off.

While trying to prevent the theft, an officer sustained non-life-threatening injuries and was taken to San Francisco General Hospital for treatment, police said in a statement.

Chase to island

The stolen police vehicle was later located traveling on city streets, and a car chase ensued, with the driver reportedly banging into cars in Glen Park and other neighborhoods before getting on the freeway and heading for Treasure Island.

Police set up a barricade at the main gate of the island just after 9 a.m., but the man drove around it, which is when two officers fired several shots at the vehicle, police said. None of the shots hit the man.

Jeff Peters, 45, happened to be on Treasure Island taking photos of San Francisco’s skyline Saturday morning when he heard a chorus of sirens coming toward him. There were also a handful of people at a nearby bus stop, Peters said, and he was surprised none was injured by the stolen vehicle or the gunshots.

“I was definitely worried about their safety,” he said. “If I was in their place, I would have been scared.”

Jump to lower deck

While the man tried to escape the island and head back toward the city, he slammed into a car at the westbound entrance of the Bay Bridge, police said. He abandoned the stolen police car and jumped to the lower deck — a fall of 30 to 40 feet — where he reportedly tried to carjack another vehicle before he was arrested. The man remains in custody, police said.

The incident shut down the western freeway entrances and exits to Treasure Island, clogging up traffic on the Bay Bridge from Oakland to San Francisco. The stolen and abandoned police sport utility vehicle remained at the exit ramp throughout the day.

The incident is being investigated by SFPD Homicide Division, SFPD Internal Affairs Division, the district attorney’s office, and the Office of Citizen Complaints, police said.

Joaquin Palomino is a San Francisco Chronicle staff writer. E-mail: jpalomino@sfchronicle.com Twitter: @JoaquinPalomino