At 6-foot-4 and 300 pounds, Michael Devlin is an imposing figure.

But the scariest thing about the burly pizza shop worker is that he never gave any reason for anyone to be suspicious of him.

The 41-year-old suspect in the kidnappings of two young boys in Missouri was an introvert who never spoke about his personal life, said Charles Wehrmeyer, an acquaintance of Devlin for roughly 15 years.

"He was more likely to talk about politics or the baseball season," Wehrmeyer told FOXNews.com on Saturday.

"He separated work and home, which is why he probably never got caught."

Devlin was arrested in the St. Louis suburb of Kirkwood Friday after a neighbor tipped police off to his white pickup truck, which police were searching for in their investigation of the disappearance last Monday of 13-year-old Ben Ownby.

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When police went to Devlin's apartment Friday, they found both Ownby, 13, and 15-year-old Shawn Hornbeck, who had been missing for four years.

"The most frightening thing is this is a normal guy," Wehrmeyer said of Devlin. "There was nothing about him that would make you think he was a monster. Which is scary, because it could be anybody. He didn't talk about sex. There was none of that."

"You meet people and the bells go off in your head," Wehrmeyer said. But he said that wasn't the case with Devlin.

"This was a guy who wouldn’t stand out in a crowd, was not loud, was not obnoxious, was just an introverted guy with a little bit of an attitude against all authority, but not much ... nothing that would ring any bells."

Neighbors at the two-story, brick apartment complex where Devlin lives agreed that he hardly appeared to be keeping secrets. He has lifelong ties to Kirkwood, a St. Louis suburb of 26,000. He has family in the area and apparently has no criminal record beyond a pair of traffic fines.

He was often seen coming and going from his jobs at the pizza parlor and a funeral home, and nothing seemed odd about a teenager seen hanging around his place.

Devlin's landlord, Bill Romer, said he was in the apartment once to fix a plumbing problem and saw a boy, apparently Hornbeck, sleeping.

"As far as I knew, that was his son living with him," Romer said. "The kid's bedroom didn't even have curtains on the windows."

Wehrmeyer said that as a counter worker and shift manager at a local pizza shop, Devlin would sometimes get frustrated "with people who didn't know what kind of pizza they wanted." But that was hardly unusual, he said.

"If I had a daughter, I probably wouldn’t let her date him," conceded Wehrmeyer, a handyman who often made repairs in the pizza shop where "Devo" worked. "But there aren’t many pizza people I would let her date."

Devlin wasn't perfect, Wehrmeyer said, but "he wasn't a monster."

Wehrmeyer said Mike Posperi, owner of the Imo's Pizza Place where Devlin was employed, first alerted the FBI and local authorities of Devlin's recently suspicious behavior. Devlin, who never missed work, didn't show up at the restaurant on Monday, the day Ownby was kidnapped. And on Tuesday, Wehrmeyer said Posperi noticed dirt on Devlin's usually clean pickup truck.

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Also suspicious was that Devlin drove to work last week. In all the years Wehrmeyer has known him, he's always walked to work and refused rides when offered.

"If you had a guy who worked next to you, if a lot of this stuff fit him, and there were police in there, you would say, 'Devo has a white truck and it had dirt on it, and he doesn’t usually drive the truck,'" Wehrmeyer said.

At the Bopp Chapel funeral parlor, where Devlin worked two days a week answering phones, he was described as a punctual but quiet worker who never discussed his private life.

"I can't tell you the feeling here," said funeral director Chris Roth. "Complete excitement for the boys being found to shock that it was him."

Wehrmeyer's son, Josh, 19, said he is angry now with Devlin because Ownby is a relative of one of his friends. But he said there was no reason to suspect Devlin was capable of kidnapping two young boys.

"He kept to himself more," Josh Wehrmeyer said. "I never had any interaction with him that said this guy is a creep."

The Associated Press contributed to this story.