Police search for apparent serial killer tied to 6 murders in California, victims' IDs released

STOCKTON, Calif. -- Six unprovoked murders of men ages 21 to 54 Since April 2021 appear to be the work of one person, according to police in Stockton, California.

Authorities are searching for a person of interest tied to the six slayings. All of the 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.

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 woman survived her injuries. A 40-year-old man was fatally shot in Oakland, California, at around 4:18 a.m. on April 10, 2021.

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 five crime scenes together.

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.

Lawrence 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."

The city of Stockton said it was putting forward a $95,000 reward for information leading to an arrest in the investigation. Stockton Crime Stoppers is posting an additional $10,000 reward. And late Monday, Stockton police increased the reward to $95,000 after an anonymous donation.

The day after Lopez's killing, Stockton police said they were not sure if the killings were related.

"(We're) still looking at it from a random point of view, but we do see some similarities," Police Chief Stanley McFadden said Wednesday. "We have been provided absolutely zero evidence that leads us to believe that one individual is running rampant in the city of Stockton killing people."

But that changed two days later when the department tied the five killings together and released an image of a person of interest.

ABC News' Caroline Guthrie and Lisa Sivertsen contributed to this report.