Police in Northern California believe a serial killer to be behind the killing of five men in Stockton and the killing of another man in Oakland based on ballistics tests.

In crimes going back more than a year, police said as many as five men in Stockton have been killed in recent months according to the same method, with all being “ambushed and shot to death alone in the dark.”

“Late Monday, police said two additional cases last year — a man’s death in Oakland and the non-fatal shooting of a woman in Stockton — had been tied to those killings,” reported KTVU. “Police would not say whether all seven shootings had been linked to the same gun.”

“Police said four of the Stockton homicide victims were walking alone and a fifth was in a parked car when they were killed in the evening or early morning in the city of 320,000 residents, located about 50 miles south of the state capital, Sacramento,” it added.

In all five of the Stockton killings, none of the men were robbed or beaten before being shot and none of the victims were personally linked. The one alleged survivor, a 46-year-old woman, was shot in April 2021 at 3:20 a.m near a tent encampment.

In Oakland, 39-year-old Juan Miguel Vasquez Serrano was killed around 4:15 a.m. in April 2021 just five days after the woman in Stockton had been shot.

“It definitely meets the definition of a serial killer,” said Stockton Police Officer Joseph Silva. “What makes this different is the shooter is just looking for an opportunity, and unfortunately our victims were alone in a dark area.”

Police have released a grainy still image of a “person of interest” while the city of Stockton, in conjunction with a local construction company owner, has offered up a $115,000 award for any information that could lead to an arrest.