Police in Tracy, Calif., say they are baffled over what drove a Sunday school teacher to kidnap and kill an 8-year-old girl, whose body was found stuffed in the woman's suitcase at the bottom of a pond.
Melissa Huckaby, 28, is in jail after being charged with the murder of the girl. Sandra Cantu. Huckaby, who lives in the same mobile home park as Sandra's family, was one of the last people to see the girl alive — when she came to play with Huckaby's 5-year-old daughter.
The girls were close friends, Tracy Police Sgt. Tony Sheneman told reporters Saturday after Huckaby's arrest.
"I couldn't even begin to theorize what her motive is," Sheneman said.
He said there are no other suspects in Sandra's murder and no other arrests will be made. He said detectives know where the crime took place, but he wouldn't say where.
Huckaby was taken into custody at 11:15 p.m. Friday night after a police interview, Sheneman said. She is being held without bail in the San Joaquin County Jail on charges she kidnapped and killed the second-grader. An arraignment is set for Tuesday.
She is on suicide watch in an observation cell, police said, and she is refusing to see visitors.
"(Huckaby) gave enough information to us during the course of the interview that probable cause was there to arrest her," Sheneman said, declining to say whether Huckaby confessed to the crime.
During the interrogation, Huckaby initially appeared "calm, cool, collected" but then became agitated and emotional, according to the sergeant. Later, she switched back to being calm, he said.
Police have not said how Sandra died. Autopsy results are pending.
Sheneman said Huckaby's interviews with the Tracy Press newspaper weren't consistent with what she had told investigators, prompting further questioning by police, though he wouldn't elaborate.
Huckaby told the paper that Sandra visited her home on March 27, the day of her disappearance, to play with her daughter. But Huckaby said she'd turned the child away because her daughter needed to pick up her toys, so Sandra went to another friend's home instead.
Huckaby also said she had left her suitcase in the driveway that day, and it was missing.
That large, dark-colored suitcase was the one in which Sandra's body was found April 6, submerged in an irrigation pond in Tracy, police said.
Huckaby is a granddaughter of Pastor Clifford Lane Lawless, whose Clover Road Baptist Church was the subject of a police search earlier this week.
"It’s not my grandfather’s," Huckaby told the Tracy Press of the missing suitcase. “It’s mine and someone took it.”
Huckaby taught Sunday school at the church and lived with Lawless in the Orchard Estates Mobile Home Park.
Lawless did not immediately respond to a call seeking comment Saturday. Sheneman said police haven't spoken with the suspect's grandfather since her arrest.
Huckaby's family had been questioned at length during the investigation, and their home and vehicles had been searched, Sheneman said.
He said the shock of learning that the suspect is a woman — and one who knew Sandra and her family — had rattled the community of Tracy, a city of 78,000 people about 60 miles east of San Francisco.
"It's unusual for a woman, statistically, to be involved in anything like this," said Sheneman.
During an early morning news conference Saturday, Tracy Police Chief Janet Thiessen said investigators worked the case tirelessly in the hopes of finding Sandra.
"We have information that Sandra, by the time she was reported missing to us, that she probably had already been murdered," said Thiessen.
"It has helped us to bring Sandra home, again not in the way that we would've hoped, but that was out of our hands shortly after she went missing."
The slain girl's aunt, Angie Chavez, said in a phone interview with The Associated Press that she was happy to learn of the arrest.
"I want to know why she did it, if she did it," Chavez said.
FOXNews.com's Catherine Donaldson-Evans and The Associated Press contributed to this report.