Melissa Huckaby, 28, was arrested before midnight Friday, about five hours after she drove herself to the local police station at the request of officers, said police Sgt. Tony Sheneman.
"She walked through the door of the police department and started a conversation (with officers)," Sheneman said at a news conference. "She was calm, cool and collected, then she became very emotional....She went back and forth from being calm to emotional."
Ultimately, she became "resigned" as the interrogation continued, Sheneman said.
"I couldn't begin to even theorize what her motive was," he said.
Police declined to say where or how the girl was allegedly killed.
The slain girl's aunt, Angie Chavez, said Sandra's mother, Maria Chavez, remains devastated despite the arrest.
"It's not over. This is just the beginning of a horrible nightmare," Angie Chavez said at the entrance to the mobile home park where Sandra lived with her mother.
"Why?" wondered Angie Chavez' husband, Joe Chavez, shaking his head. He said Huckaby should face the death penalty if convicted.
Inconsistencies in Huckaby's story led to her arrest, Sheneman said. There are no other suspects and no other arrests are expected, he said.
"Sandra was very close friends with Melissa's daughter. They used to play together," Sheneman said.
Huckaby is being held without bail at San Joaquin County Jail, and is scheduled to be arraigned Tuesday.
She is on suicide watch in an observation cell away from other inmates for her own safety, though there have been no incidents, said sheriff's Deputy Les Garcia. Huckaby is refusing visits, he said.
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.
On April 6, farmworkers draining an irrigation pond found the suitcase.
Sheneman said it was unexpected that the suspect turned out to be a woman.
"There was some speculation early on that it would be a man," he said. "It's unusual for it to be a woman statistically and according to the FBI."
Everyone who cooperated with police offered to help them locate "the monster, the man that did this," Sheneman said. Discovering it was a woman and a member of the tight knit Tracy community who knew the family was "a double blow."
"Today's going to be a very difficult day for everyone to digest that," Sheneman said.
Huckaby attended the second of the several vigils for the slain girl, Sheneman said.
"There's still a lot of work to be done in the next several weeks to ensure that Miss Huckaby pays for what's she's done," he said. "There are no other suspects in this case. We do not anticipate any other arrests in this case."
An attorney who represented Huckaby in a previous petty theft case did not immediately return a telephone message left at her home. Garcia said jail records did not reflect if Huckaby has an attorney on the new allegations.
Police said autopsy results are not yet available, and they declined to say whether investigators believe the slaying was accidental or deliberate. Sheneman said that will be an issue for Huckaby's arraignment and trial.
Police began to narrow their focus on a suspect about the same time the girl's body was found, Sheneman said. "No one person pointed their finger," he said. "It was a compilation of evidence."
After questioning, Huckaby began crying as she was handcuffed and led away for fingerprinting after 1 a.m., Sheneman said.
The girl's extended family said the investigation strained trust in the Central Valley city.
"You eye everybody with a great deal of suspicion. We're shell-shocked here," said Joe Chavez.
Susan Levy of nearby Modesto, mother of slain Washington intern Chandra Levy, appeared arm-in-arm with Angie and Joe Chavez as they spoke with reporters.
Levy said she was there to support the family as they, too, dealt with the tragic loss of a child. District of Columbia authorities recently issued an arrest warrant for a Salvadoran immigrant with sexually assaulting and killing Levy on a trail in Rock Creek Park in May 2001 in a heavily publicized case.
During an early morning news conference, 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.
Sheneman told The Associated Press that The Tracy Press' published interviews with Huckaby revealed inconsistencies that prompted further inquiries from investigators.
Huckaby had previously told The Tracy Press that Sandra visited her home on the day of her disappearance to play with her 5-year-old daughter. But Huckaby said she'd turned Sandra away because her daughter needed to pick up her toys and Sandra went to another friend's home. Huckaby also said she had left her suitcase in the driveway that day, and that it was missing.
Sheneman confirmed early Saturday that the suitcase that held Sandra's body belonged to Huckaby.
The Tracy Press reported that Huckaby was released Thursday from Sutter Tracy Community Hospital, where she spent several days in intensive care for what she described as "internal bleeding."
Huckaby is a granddaughter of Pastor Clifford Lawless, whose Clover Road Baptist Church was the subject of a police search. Huckaby taught Sunday school at the church and lived with Lawless in the Orchard Estates Mobile Home Park that also was Sandra's home.
A phone call to Lawless was not immediately returned.
Huckaby's family had been questioned at length during the investigation, and their home and vehicles had been searched, Sheneman 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.
In an interview with the newspaper on Friday, Huckaby said someone else by the same name was facing charges for the attempted November theft from Target.
California Department of Corrections and Rehabilitation spokeswoman Terry Thornton said Huckaby has no state prison record.
Huckaby 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."
Barbara Sokoloski, 69, whose home is behind Sandra's, said she is glad an arrest was made. She described Sandra as "a friendly sweet little girl who always went around trying to find somebody to play with."
"It's too bad that kids these days can't go out and play like we did when I was a little girl," she said.
Witness saw strange activity near irrigation ditch
Police earlier said they were looking into a tip from a man who said he saw a strange truck in the area where Sandra's body was found, a few days before it was discovered.
"We don't really get many people down that road, so it was something I remember and something I thought was suspicious," said Tracy resident Stephen Memory.
19-year-old Memory lives just down the road from the irrigation ditch where Sandra's located on Monday. A Stockton police cadet told ABC7 three days before the discovery that he saw a strange man in a pickup truck that was faced the wrong way, by the side of the road.
"It was a Chevy Silverado with a couple inch lift on it with wider set tires, and it was tan colored, a newer model Chevy Silverado with a 40 to 50-year-old man in the car by himself. He was wearing a baseball cap. He didn't want to look at me too much," said Memory.
Memory says the FBI did take his information. Tracy police did not confirm if the sighting near the irrigation pond figures into their investigation.
In the meantime, Sandra's body was released from the San Joaquin County Coroner's office. She will be interred at the Tracy Mausoleum. A marker with the little girl's name on it is being prepared. The public place for mourning has also moved from the mobile home park where Sandra lived to Fry's Memorial Chapel.
Fry Memorial Chapel will be open through the weekend.
Public Grieving Place:
Fry Memorial Chapel
550 South Central Avenue
Hours: 10-4 on Saturday, Sunday and Monday
Public Service for Sandra Cantu:
Thursday, April 16, 2009
1 p.m. - People are asked to arrive early since there will be limited parking
Merrill F. West High School
1775 West Lowell Avenue
The reward for information leading to an arrest in Sandra's case has risen to over $30,000.
Anyone with information is urged to call the Tracy Police at: 1-209-831-6TIP
The Associated Press contributed to this report.