Underwood was being held Saturday in the McClain County Jail on a complaint of first-degree murder, a jail official said.

The district attorney called Jamie's killing one of the most "heinous and atrocious" crimes he'd seen in his career as a prosecutor. He said he planned to file first-degree murder charges against Underwood on Monday and would seek the death penalty.

"This does not appear to be a spur-of-the-moment crime of opportunity but a well-thought-out, premeditated act with months of planning and preparation," Kuykendall said.

Tompkins said Underwood had no apparent criminal record. He also said it wasn't known whether Underwood had a history of mental illness, but he expects mental competency to be an issue at trial.

It was not immediately known whether Underwood had a lawyer.

The manager of the apartment complex, Tim Bayer, told The Oklahoman that Underwood liked to stand outside his apartment and watch children play. He said Underwood didn't have a car of his own and that he kept his apartment clean.

Jamie lived upstairs in an apartment with her father, Curtis Bolin, an auto mechanic, her grandmother said. Jamie's mother, Jenny, is a truck driver in Oklahoma City. The couple separated several years ago, Fox said.

Fox said the family is distraught, especially the child's father, who remained under sedation.

"His whole life revolved around Jamie," Fox said. "He didn't go out and party. He didn't drink or smoke. This has probably destroyed him."