Police officer Gary Wagster spent all night Thursday watching Michael Devlin's apartment. He suspected Devlin might be holding 13-year-old Ben Ownby captive inside, and Wagster was worried what the 300-pound (135-kilogram) man might do to the boy.
"Did I sleep? No," Wagster said.
Wagster's suspicions ultimately ended one of the United States' strangest kidnapping cases and improbably brought Ownby and Shawn Hornbeck - another eastern Missouri child missing since 2002 - back to their families.
Suspicion had started earlier that Thursday when Wagster and his partner saw that Devlin's truck matched the description of one seen speeding from the site of Ownby's disappearance last Monday.
A neighbor said the truck belonged to Devlin, and the officers saw him leave his apartment to empty his trash into a trash bin. They questioned Devlin in the parking lot, and he was friendly and cooperative.
Devlin's demeanor quickly changed when the officers started asking him specific questions, Wagster said. He became agitated and defensive.
"It was a total 180 degrees from where he was," Wagster said.
With red flags raised, Wagster reported the find to FBI agents and Franklin County sheriff's deputies who were leading the hunt for Ownby.
When agents arrived Thursday evening, Devlin would not let them into his apartment, according to a law enforcement official familiar with the investigation, who refused to be identified because he is not authorized to speak publicly about the case.
By the time Devlin, a pizza parlor manager, left for work Friday morning, local police had staked out his apartment and the FBI agents were investigating him.
FBI agents walked into Imo's Pizza in Kirkwood Friday morning to interview Devlin. A probable cause statement said Devlin admitted to kidnapping Ownby, who vanished days earlier after getting off the school bus near his home in Beaufort, Missouri.
When agents entered Devlin's apartment, they found Ownby inside. They also found Hornbeck. Authorities at first did not recognize Hornbeck, who disappeared at age 11 while on a bike ride but was now a gangly 15-year-old with floppy hair and a pierced lip. He told them his identity when agents entered the apartment.
Devlin is jailed on $1 million (EUR 780,000) bond and awaiting arraignment on one charge of kidnapping. More charges are likely, authorities said.
But the arrest raises more questions than it answers.
Authorities will not say how Devlin kept the boys confined in his home. Hornbeck seemed to have had every chance to escape during his captivity. He was left alone for hours to ride his bike, play video games and walk past missing-child posters showing his own age-progressed image.
But mental health experts say this troubling case is hardly so simple, and that Hornbeck was likely kept mentally shackled by terror and domination from the man accused of kidnapping him.
"I think it's a real mistake to judge this child. Whatever he did to this point to stay alive is to his credit," said Terri Weaver, an associate psychology professor at Saint Louis University.
Weaver, an expert on post traumatic stress disorder, said children in such situations kick into survival mode, "doing what needs to be done to keep yourself going day-to-day."
Internet profiles posted as far back as two years ago that were created using pictures of Hornbeck emerged over the weekend when a blog mentioned them. A Kirkwood detective said Sunday that he had heard about the profiles but did not know what role they might be playing in the investigation, the AP says.
Neighbors described Devlin as a loner with a quick temper, and said they often heard banging, shouting and arguing coming from his apartment.
It was unclear Sunday whether Devlin had a lawyer. Jail officials would not comment, and the county public defender's office was closed.
The families of both boys have refused to comment beyond a pair of news conferences they held Saturday, during which the boys were told not to talk to reporters. Lawyers for the families did not answer phone calls to their offices Sunday.