Melissa Huckaby, 28, was arrested early Saturday morning and charged with kidnapping and murder.
Huckaby's grandfather is pastor of the Clover Road Baptist Church, near the mobile home park where Sandra Cantu's family lives. Police searched the church Friday in the hours before Huckaby was arrested, filling a van with evidence bags.
Police and residents in Tracy responded with shock when the suspect in the murder of a young girl turned out to be a woman, the mother of the slain girl's best friend.
Melissa Huckaby was on suicide watch Saturday at the San Joaquin County Jail, where she is held on suspicion of kidnapping and killing 8-year-old Sandra Cantu. The girl's body was found in one of Huckaby's suitcases in an irrigation pond nearly a week ago, police said.
"This was an anomaly in the murder of a child," police Sgt. Tony Sheneman said at a news conference Saturday. "Finding out that it is a woman who is responsible for Sandra's kidnapping and murder, and then finding out it is a member of the community is another blow."
FBI statistics show women are involved in just 7 percent of murders of any sort. Solo killings of children by women are even more unusual.
"A review of data from the 2007 Uniform Crime Report confirms that the arrest of Melissa Huckaby in the Sandra Cantu murder investigation is uncommon," said FBI spokesman Steve Dupre in Sacramento.
Sandra disappeared on March 27 and hundreds of volunteers and law enforcement officials turned out to search for her. Pictures of the girl with dark brown eyes and light brown hair were posted all over Tracy, a city of 78,000 people about 60 miles east of San Francisco. Police said they received 1,500 tips in the hunt for Sandra and her killer.
"It's very unusual for women to be involved in an abduction and murder of a child," said Candice DeLong, a retired FBI profiler based in San Francisco. "Sometimes we see this when the woman is working with a male partner. It does not appear to be the case this time. But this was not a sexually motivated crime."
Huckaby attended the second of the several vigils for the slain girl, Sheneman said.
On April 6, farmworkers draining an irrigation pond found the suitcase.
Sheneman said investigators have no motive for the slaying, which drew national attention. Police declined to say where or how the girl was allegedly killed. Inconsistencies in Huckaby's story led to her arrest, Sheneman said.
There are no other suspects and no other arrests are expected, he said.
Huckaby is a granddaughter of Pastor Clifford Lawless, and taught Sunday school at the Clover Road Baptist Church. She lived with Lawless in the Orchard Estates Mobile Home Park that also was Sandra's home.
Huckaby's uncle, John Hughes Jr. of Whittier, said his niece was from a good home, but had hit a rough patch in her life and moved in with her grandparents in Tracy to get past her troubles.
"They opened their home up to her to try to get her life back on track. I think a lot of families have problems like that," Hughes said.
Huckaby was scheduled to appear in court on April 17 to check in with a county mental health program as part of a three-year probation sentence for a petty theft charge to which she pleaded no contest.
She was arrested about five hours after she drove herself to the local police station at the request of officers. She is being held without bail for an arraignment Tuesday.
"She was calm, cool and collected, then she became very emotional," Sheneman said.
The slain girl's family was as puzzled as police.
"Why?" wondered her uncle, Joe Chavez, shaking his head. He said Huckaby should face the death penalty if convicted.
It was not immediately clear if Huckaby had hired an attorney.
Police said autopsy results are not yet available, and they declined to say whether investigators believe the slaying was accidental or deliberate.
She had worked as a checker at a Food for Less grocery store in a strip mall just east of the mobile park for nearly four years, until she was fired sometime in 2004, said Matt Duncan, an assistant manager at the store now known as FoodMaxx.
"I wouldn't have anything bad to say about her, until now," said Duncan, who has worked at the store off-and-on for about 10 years. "I would've never suspected her to do something like this."