Williams had his first court appearance Wednesday, and his arraignment was moved to next Friday.
RELATED: Mother and daughter shot and killed in Antioch
At 4:30 a.m. on July 5, 55-year-old Valinda Scott and her 28-year-old daughter, Milan Ardoin, were shot and killed in their Antioch neighborhood. Ardoin's colleague posted on Facebook that she worked closely with 3rd Street Youth Center and Clinic in San Francisco's Bayview neighborhood.
She leaves behind a 4-year-old son.
Scott Alonso, a spokesperson with the Contra Costa County DA, said investigators are looking into exactly how Williams knew the victims.
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"That's something we're still looking into with Antioch police," Alonso said. "There's nothing I can give publicly yet, but it's one of the items we certainly pursue. In a homicide like this, we want to understand about the motivations, how the victim knew the defendant and where that can lead us, so it's certainly something we're taking a look at."
Williams is being held without bail.
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The DA's Office thanked Oakland Police Department for its help in arresting Williams.