A former employer of the caregiver tipped off police to Warrick's location in Pacheco. Until Wednesday, Warrick was living with Scanlon, a woman confined to a wheelchair with apparently no idea about her new caregiver's violent past.
According to Pleasant Hill police, Scanlon hired the woman that killed her off of Craigslist. Police say Warrick stabbed Scanlon in her home sometime Wednesday.
While police searched a nearby creek for evidence, investigators would not say if they have a murder weapon, or a motive.
"She has been interviewed, but I can't discuss the content of the interview," said Pleasant Hill Police Lt. Dan Connelly. "I will say that she has been cooperative."
Warrick was arrested Thursday at a mobile home in Pacheco. Scanlon's van was found parked in the driveway. Until recently, Warrick cared for an elderly woman who lived there, but that woman passed away and according to her family, Warrick was not supposed to be staying there.
"To know that she was living right next door, I don't know how long she was living there, but it really makes you stand back and think," said neighbor Len Shaffer.
In 1997, Warrick stormed the Napa State Hospital, took hostages and exchanged gunfire with sheriff's deputies. Charged with 18 felonies, including five counts of attempted murder, Warrick was convicted in 1999, but a jury found her not guilty by reason of insanity.
She was committed to a state hospital in San Bernardino until 2002, when Napa Judge Stephen Kroyer found her sane, no longer a danger to the community, and released her to an outpatient program in Contra Costa County.
Thursday, Napa County district attorney Gary Lieberstein told ABC7, "At that time, she was a troubled young woman who needed to be locked up for life. We lost that opportunity."
At Scanlon's house, neighbors came by with flowers.
"In her motorized wheelchair, she used to go up and down the street, she was always friendly with everybody," said neighbor Joanne Branshaw. "She waved at the kids... and was just really a nice, pleasant person,"
Warrick's most recent employer in Pacheco, the family she worked for before she went to live with Scanlon, say they came by Warrick by recommendations from friends. They say she came highly recommended, and that while she was working for them, she was every bit the loving caregiver.