ST. PETERSBURG — Shortly before 4:30 p.m. Sunday, the Florida Department of Corrections received a standard alert.

An inmate from a work release center on Gandy Boulevard had cut or tampered with her ankle monitoring device.

Last year, the FDC logged 73 inmate escapes. At first, nothing seemed unique about this one. The woman was labeled an escapee, and the Pinellas County Sheriff's Office was notified.

But Christal Anderson, authorities said, was a model inmate. Anderson, 34, had been on an approved visit to the house she once shared with the father of her 6-year-old son.

When investigators spoke with the father, Michael Paul Brown, he said she snapped the bracelet and took off after the couple had argued.

It wasn't until Thursday that a St. Petersburg police SWAT team found Anderson's lifeless body tucked into Brown's closet. He was dead from a self-inflicted gunshot wound, flat on the floor under his bed.

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When the tampering alarm on Anderson's ankle monitor sounded, officials at the Suncoast Community Release Center on Sunday called the cellphone tethered to the device, a spokeswoman said.

Brown, 37, quickly called back and told them he did not know where Anderson had gone, said Jim Previtera, St. Petersburg's assistant police chief.

A few minutes passed, Previtera said, before the GPS anklet began "to move around a little bit."

Corrections officials tracked the device to the 4100 block of 16th Street N, he said. The signal did not move until the battery died early the next morning. Investigators still had not found the device Thursday afternoon.

Later Sunday, an employee from Suncoast, a private program run by Goodwill, went to Brown's house at 3328 21st St. N and talked to him, said McKinley Lewis, a spokesman for the FDC. He stuck to his story, and no one from Suncoast entered the home.

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Anderson was convicted in 2014 of fraud and sentenced to three years in prison for taking tens of thousands of dollars of jewelry from her employer, the International Diamond Center.

While in state custody, she racked up no infractions.

"This was a woman who was paying her dues for what she did," Previtera said. "She was obeying the rules and obviously trying to get her life back on track."

Anderson was transferred to Suncoast last October, according to state records. The work release center at 10596 Gandy Blvd. hosts female inmates who receive counseling and work 35 hours a week. Anderson had been employed for months at Ameri-Pride in Clearwater.

When investigators started talking to women at Suncoast and Anderson's co-workers, Previtera said, Brown's story unraveled.

Anderson's friends told investigators that she was afraid of Brown. One or two weeks before, they said, she showed up with bruises. Brown was erratic, Anderson had said, and he had threatened her.

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Suncoast and the FDC notified St. Petersburg police Wednesday that Anderson's disappearance was suspicious.

After 5 p.m., undercover detectives began surveillance outside the house at 3328 21st St. N, Previtera said. Brown's relatives showed up to drop off the couple's 6-year-old boy. Officers kept the child outside, Previtera said, but the relatives went in.

They returned with a note, slid under the bedroom door: Brown was inside. Anderson, too.

Police sent a heavily armed special weapons and tactics team to surround the house. The standoff spilled into the night. At some point, Brown texted a family member that Anderson was dead, Previtera said. Hostage negotiators talked to him sporadically. After midnight, police tried to use tear gas to flush him out.

They pulled back, Previtera said, after they thought they heard two gunshots inside.

Police eventually used a robot to check the home. They saw Brown lying motionless under the bed, Previtera said.

A tactical team burst into the bedroom with a flashbang stun grenade. They heard a single gunshot. Brown apparently killed himself, Previtera said.

Anderson had been dead for days, he said. Investigators could not immediately determine her cause of death.

"He more likely than not killed her on Sunday, probably after an argument," Previtera said. "Why he held the body and disposed of the body the way he did, we'll never know."

Detectives are not sure if the couple's son was home Sunday or during the following three days. The family could not be reached for comment.

"Ms. Anderson was preparing to re-enter society. She had done well in the program," Suncoast said in a statement Thursday. "It is heartbreaking that she will not have that opportunity."

Times staff writer Claire McNeill and senior news researcher John Martin contributed to this report. Contact Zachary T. Sampson at zsampson@tampabay.com. Follow @ZackSampson.