"A mission to kill. At these scenes, there have been wallets keys. This person could easily be taking vehicles, money, credit cards. But none of that stuff has been taken," explains McFadden.
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Chief Mcfadden was interviewed on GMA 3 on Thursday morning. He says there have been seven shootings - six fatal. As he explains, a woman who survived one of the shootings, has been extremely helpful in creating a suspect profile.
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"She did let us know it was a male suspect. She was able to provide us with a height and weight, and that's what we connected with us with the video that we are pushing out," says McFadden.
That surveillance video shows a person of interest with a distinct limp. Police have placed the person of interest at several of the shootings. They say they don't have a motive, but there are some similarities with each shooting.
"What we can tell you, the location, the environment are very consistent. It's very dark locations. It is locations where there are not many witnesses around. It is locations where it is overshadowed by trees. This is a person that lurks in the shadows," says Chief McFadden.
In addition, police say most victims have been ambushed late at night. And most are Latino. Based on those patterns, the Alvarado family is making big changes.
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WATCH: Experts weigh in on Stockton serial killer, their next possible move
Experts weigh in on Stockton serial killer, their next possible move
"My dad is the one who commutes to the Bay Area. He is the one who wakes up at three, four in the morning to commute. So it's been our concern with him, especially since Hispanics are especially the ones who have been getting (targeted)," says Karen Alvarado.
She says they are installing security cameras around the house. And making sure their dad parks in the driveway.
"To make sure that we can at least see what's going on. And we have been telling him to go in and out real quick. No staying in the car, just hanging out. Just do what you need to do and head out," she says.
"We are curious, of course. It is kind of weird, daunting," says Serena Miller, a long-time Stockton resident. "We were in Hawaii in August and I was like, 'Oh, another (person) died.' And it kind of hit me, I was like, 'Oh, that's all this.'"
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Miller says she understands the threat and the challenges this case presents for Stockton police. But she admits, that her family has become desensitize to the violence in Stockton.
"What can they really do? I mean, look at our city! I mean, (the police) have a lot to do," says Miller.
Stockton police says they are working with state and federal officials on this case.
A reward of $125,000 is being offered for any information that leads to an arrest.