A series of homicides in Stockton, California, has forced local police to launch an investigation into the serial killings. 

Police Chief Stanley McFadden said at a news conference Wednesday that all the victims were killed while outdoors alone late at night.

“We do see some similarity where it’s really areas of darkness, it’s really areas where the person is by themselves, maybe not even knowing it’s coming, and that’s kind of what (we’re) looking into in some of the most recent ones,” McFadden said Wednesday. He did not mention the number of homicides that have the same pattern. 

“We do not know if it is one suspect or multiple suspects,” police said in a statement.

Four fatal shootings have been reported in Stockton in September, and six reported since Aug. 28. 

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On Tuesday, Sept. 27, a man was found laying on a sidewalk on Porter Avenue with fatal gunshot wounds. On Sept. 21, a man was found dead on a sidewalk near Manchester Avenue and Rosemarie Lane, police said.

In a Sept. 20 homicide on Sikh Temple Street, the victim was found shot in a vehicle, according to police.

“I know there’s been talk on media and social media that there’s a serial killer in the city of Stockton,” McFadden said. “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.”

While police highlighted the similarity of the homicides occurring at night to isolated victims, they also mentioned that the killings took place in areas with tree cover, low lighting and no cameras or witnesses.

None of the victims were robbed, McFadden said at the news conference.

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Police advised residents to travel in groups at night, or stay indoors if possible.

“I’d appreciate if we could all be reviewing our (security) cameras, (to) see what’s happening (at) night,” McFadden said. “Could it be one person? I guess it could be. Could it be multiple people? Absolutely.”

State and county law enforcement are assisting in the investigation, he said.

Anyone with information was asked to call 209-937-8377 or 209-937-8323. People can also call Stockton Crime Stoppers at 209-946-0600 with any tips that could lead to a reward of up to $10,000.