Randall Hopley, 46, was arrested in a remote area near Crowsnest Pass, a short drive away from Kienan's home in Sparwood, B.C.
"It doesn't get any better than this," a smiling Insp. Brendan Fitzpatrick told a news conference.
Kienan vanished nearly a week ago from his two-storey house, and it was there that he mysteriously reappeared this past Sunday.
The boy's disappearance prompted a massive search around the home, an Amber Alert that eventually spanned two provinces and days of breathless headlines across the country as the public and Kienan's family hoped he would be found safe.
Fitzpatrick said a tip led police to an area near Crowsnest Lake, not far from a local bible camp. Fitzpatrick said the Mounties arrived Monday night, a perimeter was set up and police dogs began combing the area.
By Tuesday morning, the dogs had reached a set of abandoned mining cabins.
"As one (of the dog handlers) knocked on the door, the dog indicated that there was possibly some activity, and the dog master and the police dog pursued that and it resulted in Mr. Hopley being arrested in a short chase," said Fitzpatrick.
Hopley was arrested for kidnapping and abducting a child under 14, said Fitzpatrick.
He was being held in Cranbrook, located about 70 kilometres southwest of Sparwood, and was to make his first court appearance Wednesday morning. Hopley has also been charged with two counts of breach of probation during the past week, court records indicate.
The arrest marked the end of a long week for the more than 150 officers involved in the case, many of whom have been working 20-hour days since it began, said Fitzpatrick.
"I can tell you that this is one of the best days that these investigators out here have seen," he said.
"To have that child found in the middle of the night on Sunday was absolutely exhilarating, and now to tell the community that we have this man in jail and they can go back to their normal course of business is a very proud moment for the RCMP."
Police have said Kienan's parents put him to bed last Tuesday night, only to discover he was missing the following morning. The family reported his disappearance to police, who immediately launched a search from the ground and air. The Amber Alert naming Hopley as a suspect was issued Wednesday evening.
Kienan's father, Paul Hebert, said he was relieved when he heard of the arrest and has already forgiven Hopley.
"There's two ways that you can look at it: You can feed hate or you can feed love. They're both characters. Hate is a very hungry animal and I just don't choose to feed that animal," Hebert told reporters earlier in the day.
"He's a man that needs help."
Hebert has been critical of the justice system for failing to intervene as Hopley amassed a lengthy criminal record, including one case that included allegations involving a child.
In 2008, Hopley pleaded guilty to break and enter and was sentenced to 18 months in jail. A Crown spokesman has confirmed Hopley admitted in court that he attempted to take a 10-year-old boy from a home in Sparwood, although charges of unlawful confinement and attempted abduction were stayed.
In the 1980s, Hopley was convicted of sexual assault and sentenced to two years in federal prison, though few public records are available to confirm the nature of those allegations.
The RCMP also used Tuesday's news conference to respond to critical news coverage about how the force handled the case, specifically the timing of the Amber Alert and how someone was able to enter the Hebert's empty home undetected when Kienan was returned.
Much of the news coverage of the case has focused on the Amber Alert, with reporters questioning why it wasn't issued sooner and why it took several days before it was expanded into Alberta.
When Kienan was reported missing, Fitzpatrick said police immediately examined the possibility of issuing an Amber Alert while search teams combed the area around the family's home.
Fitzpatrick explained the case did not yet meet the threshold to activate the system -- a set of criteria that wasn't met until police identified Hopley as a suspect.
And while the Amber Alert was extended into Alberta on Saturday, Fitzpatrick insisted the media coverage of the case had already achieved the same effect.
"At our earliest opportunity, when the threshold had been met, the Amber Alert was activated," said Fitzpatrick.
"The minute that Amber Alert was activated, I was monitoring the Internet and the news, the coverage was extensive in Alberta -- it had arguably as good coverage or better than we saw in British Columbia."
He acknowledged police weren't watching the Hebert home when Kienan was returned, but he said there was no reason to believe that would happen.
"I will say that the probability that Kienan be returned to his residence is extremely low. It's a virtually unprecedented situation," he said.
Hebert has said he left the home unlocked hoping Kienan would be returned there, though he hasn't said whether he did so on the advice of police.
Sharon Fraser, Sparwood's acting mayor, said she hopes news of the arrest helps her community move on after what she described as "the longest week in Sparwood."
"My God, maybe now we can get back to some reality and normality, you know?"
Still, Fraser said Kienan's disappearance taught Sparwood residents some difficult lessons and she suggested life may never return completely to normal.
"This is one of the hardest lessons all of us have had to learn, that we can't leave our doors unlocked and we can't let our children just run."
-- With files from James Keller and Keven Drews in VancouverSuggest a correction