The Oakland man so far appears to be the only victim outside of the Stockton area linked to the same killer.
Juan Vasquez Serrano, 39, was fatally shot on Harmon Avenue in Oakland on April 10, 2021, according to the Alameda County coroner.
Authorities now say it appears he was killed by the same individual who has been tied to the fatal shootings of five men in Stockton, in addition to the shooting on April 16, 2021 of a woman in Stockton who survived.
Ballistics tests have linked all seven shootings, authorities say, though it hasn't been determined if they were all the work of a single person.
There's now a $115,000 reward for the killer's arrest.
All of the fatal victims were men and all were alone at the time they were fatally shot, police said. The killings all happened at night or in the early morning hours.
Police released only a few details about the string of murders and when they happened: a 35-year-old man fatally shot at 12:31 a.m. on July 8; a 43-year-old man fatally shot at 9:49 p.m. on Aug. 11; a 21-year-old man fatally shot at 6:41 a.m. on Aug. 30; a 52-year-old man fatally shot at 4:27 a.m. on Sept. 21; and a 54-year-old man fatally shot at 1:53 a.m. on Sept. 27.
On Monday, San Joaquin County's Office of the Medical Examiner identified the victims. Paul Yaw, 35, was killed on July 8; Salvador Debudey Jr., 43, died on Aug. 11; Jonathan Hernandez Rodriguez, 21, was killed on Aug. 30; Juan Cruz, 52, was the Sept. 21 victim; and Lawrence Lopez Sr., 54, was slain on Sept. 27.
While detectives continue to follow up on this series, they confirmed two additional cases from April 2021 that believed to be linked, with one tied to the Bay Area.
Police say a 46-year-old woman was shot at Park Street and Union Street in Stockton at around 3:20 a .m. on April 16, 2021. The women survived her injuries. She was able to give police a description of a male suspect wearing all dark clothing, wearing a face mask and standing around 5'10 to 6 feet tall.
Serrano was fatally shot in Oakland at around 4:18 a.m. on April 10, 2021.
Stockton police released surveillance video of a person of interest in the investigation. They said it isn't clear yet if the person is a suspect or just a witness. The video does not show the person's face, but police point out he has an uneven gait and an upright posture.
Stockton serial killer: Police release surveillance video of man linked to 7 shootings
Stockton police told ABC News that all of the victims were ambushed, none were robbed and none of the incidents were drug- or gang-related. Police also told ABC News they have physical evidence linking the crime scenes together.
Lorenzo Lopez "was just a person who was out here at the wrong place at the wrong time at the wrong circumstance," his brother Jerry Lopez told ABC Sacramento affiliate KXTV. "It's hard to process that this has happened. I mean, me and my brother have been like twins. We were a year a part so we were pretty close."
Paul Yaw "was a good boy who grew into a good man with a big heart. He will always live on in our hearts. He was always there for you if you needed him," the family said in a statement to ABC News. "He was a son, brother, father, grandson, nephew and cousin. I still can't believe he's not coming back."
ABC News' Caroline Guthrie and Lisa Sivertsen and The Associated Press contributed to this report.