The gunman is on a 'mission to kill,' Stockton Police Chief Joe McFadden told ABC News.
STOCKTON, Calif. -- Authorities in Northern California are searching for an apparent serial killer tied to six fatal shootings.
No motive is known, Stockton police said, but the slayings appear to be intentional and are linked by ballistic evidence.
The gunman is on a "mission to kill," Stockton Police Chief Joe McFadden told ABC News' "GMA3" on Thursday.
The suspect could've "easily taken vehicles, taken money, credit cards, but none of that stuff has been taken," he said. "It seems that this person or persons is very focused on the killing -- and very calm and confident afterwards."
All of the victims were alone, police said, and the killings happened at night or in the early morning.
"What we seem to have in common is probably complexion -- it has been folks that are different races, but they have a similar complexion," the chief continued. "The location, the environments have been consistent: It's very dark locations, it's locations where there's not very many witnesses around."
"This is a person that lurks in the shadows," McFadden added. "Our victims are being caught by surprise."
Here's how the crimes unfolded:
At 4:18 a.m. on April 10, 2021, a 40-year-old man was shot and killed in Oakland, California. Stockton police announced on Monday that this killing has been linked to the spree; all of the other attacks were in Stockton.
Days later, on April 16, 2021, at 3:20 a.m., a 46-year-old woman was shot in Stockton and survived her injuries, police said.
She told officers she was in her tent and heard someone approaching. She came out to find someone holding a gun, police said. Multiple shots were fired but the shooter didn't say anything, she told police.
This shooting has also been linked to the spree, police said.
More than one year went by.
Then on July 8 at 12:31 a.m., a 35-year-old man, Paul Yaw, was fatally shot in Stockton, police said.
Yaw "was a good boy who grew into a good man with a big heart," his family said in a statement to ABC News. "He was a son, brother, father, grandson, nephew and cousin."
Weeks later, on Aug. 11 at 9:49 p.m., a 43-year-old man, Salvador Debudey Jr., was shot and killed, police said.
The next victim was 21-year-old Jonathan Hernandez Rodriguez, who was fatally shot at 6:41 a.m. on Aug. 30 in Stockton.
A 52-year-old man, Juan Cruz, was fatally shot in Stockton at 4:27 a.m. on Sept. 21, police said.
The final victim was 54-year-old Lawrence Lopez Sr., who was was fatally shot at 1:53 a.m. on Sept. 27, according to police.
Lopez was a musician who leaves behind six children, Jerry Lopez, his brother, told ABC News.
"It's mind-blowing that the deaths are supposedly connected," Jerry Lopez said.
On Sept. 30, Stockton police announced they believed the five 2022 homicides were linked, adding that they met the definition of a serial killer.
Police released this image of a man who is considered a person of interest.
On Oct. 3, police said they believed the two 2021 shootings -- one fatal and one non-fatal -- were also linked.
On Oct. 4, Stockton police released a short video of a person of interest.
McFadden said it's unclear if the person of interest in the video "is a suspect or a witness, but it's an individual that we have seen at more than one scene."
Police ask anyone with information to call Stockton Crime Stoppers at 209-946-0600.
ABC News' Zohreen Shah, Alyssa Pone, Jenna Harrison Esseling and Caroline Guthrie contributed to this report.