Police have linked several shootings to a possible serial killer in Stockton, Calif.

Stockton Police have now linked seven shootings — six fatal — to a possible California serial killer who remains at large.

Officials confirmed that the string of seemingly random homicides began in April of last year — more than a year earlier than previously believed — and they warned there could be additional victims.

Police have drawn connections to all seven shootings by using ballistics evidence and checking that against a statewide database, as well as surveillance video footage from some of the crime scenes.

"So, as the investigation continues, there's definitely a possibility that there could be more," Stockton Police Public Information Officer Joe Silva told NPR.

A team of detectives is scouring older shooting homicides for potential links to the recent spate of violence, according to Silva. The department has also called on other local precincts to peruse their own cases for matches.

A survivor offers few details about the shooter and police have few tangible leads

Last week, authorities stated that a serial killer may be responsible for recent shooting deaths that have shaken residents of Stockton, which occurred between July 8 through Sept. 27. They also said that the victims had all been men within the city limits. But now, new information indicates that a 40 year-old Hispanic man, who was fatally shot on April 10, 2021 in Oakland, is linked to the more recent shootings.

It would be the first of the serial killings outside of Stockton.

Additionally, police have connected the April 16, 2021 shooting of a 46 year-old-Black woman in Stockton to the suspect. Unlike other victims, she is the only person to have survived her injuries, and the only woman who appears to have been targeted.

"Our detectives have been working with her to find out as much as we can," Silva said, noting that it is possible there is more than one shooter involved in the string of homicides.

"She described her shooter as an unknown race male, 5'10" to 6 feet tall with a slim build," Silva said. On the day of the attack, he was wearing a dark colored sweatshirt with the hood pulled up over his head, dark pants, and a black face mask.

"What's weird is that, even though we're working around the clock and we're getting lots of calls and tips, right now we don't have any workable leads," Silva said.

Officials release video footage of a person-of-interest

Stockton police are working alongside several local and federal agencies to identity and capture the perpetrator or perpetrators, including the FBI, California Highway Patrol, several local sheriff's departments, and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The five victims who were slain in recent months have been identified by the San Joaquin County's Office of the Medical Examiner: Paul Yaw, 35, who was killed on July 8; Salvador Debudey Jr., 43, who died on Aug. 11; Jonathan Hernandez Rodriguez, 21, who was fatally shot on Aug. 30; Juan Cruz, 52, the Sept. 21 victim; and Lawrence Lopez Sr., 54, who was killed on Sept. 27.

After reviewing many hours of video surveillance, investigators believe they have located a "person of interest," the department announced in a statement that included a grainy screengrab of an unidentified person dressed in a dark hoodie and dark pants. On Tuesday, officials released a short video of the same person, whose face is never captured by the camera.

In every case, including the incident in Oakland and the attack on the woman last year, Silva said all of the victims were out late at night or in the early morning hours, alone and in poorly lit areas.

"That's when they were ambushed," he said. None of the cases involved robbery or are believed to be gang-related, he added.

Police are urging the public to contact the department with information related to the killings. As of Tuesday, there is a $125,000 reward for information leading to an arrest.