Police in Ottawa allege 52-year-old Scott Waldo Fraser would then post photos and videos of the assaults on the Internet.
"He would befriend the young boys on the street, and make them offers of playing video games or having snacks at his residence," said Ottawa police acting Staff Sgt. Francois D'Aoust.
In April, the U.S. Postal Inspection Service tipped off police in Toronto about a Canadian who was suspected of abusing boys and sharing images of the assaults.
Peel Regional Police searched a Brampton house in May and arrested Fraser. He faces 42 charges, ranging from sexual assault to making child pornography and extortion.
The alleged assaults took place in the Ottawa area between 2002 and 2008 and allegedly involved five boys aged 9 to 17.
D'Aoust said Fraser lived in the west end of Ottawa, and worked in a job where he had no access to children and was not in a position of authority.
Police are now combing through several computers and an external hard drive, D'Aoust added. He said they're dealing with "hundreds of thousands" of images, but it is not yet known how many — if any at all — are child pornography.
It is unclear if Fraser actually sent the alleged photos and videos through the mail.
"It was definitely peer-to-peer, or online," D'Aoust said. "I'm not sure of the U.S. Postal Service investigation, but I know that some or most images were posted online, or shared online."
Fraser is scheduled to appear in an Ottawa court on Aug. 2.