But while the young man in the video, Andre Poulin, cast himself as just a typical Canadian, the authorities there say he lived a far different life from the one he described. In his late teens and early 20s, according to a Canadian prosecutor, Mr. Poulin learned how to build explosives online and considered becoming an anarchist or a Communist, before converting to Islam.

And the video goes on to show where his beliefs ultimately led.

After Mr. Poulin — later known as Abu Muslim — finishes his monologue, he is seen running through a field in Syria during a siege of an airport, then dying in the battle. A graphic picture of his corpse is shown, and he is hailed as a martyr. He was likely 24 at the time of his death last year.

The video is believed to be one of the first pieces of media in which the Islamic State in Iraq and Syria — or ISIS, the group that controls large parts of both countries — used an English-speaking North American to try to lure others to fight on its side. It was distributed recently by a propaganda arm of ISIS, known for having one of the slickest and most aggressive media operations in the Islamic world, according to experts who track jihadist materials.

As its fighters have gained more territory in Iraq and Syria, ISIS has taken over World Cup hashtags on Twitter to spread propaganda screeds and used Facebook to generate death threats.

“Once ISIS expanded into Syria, it was forced to compete with a lot of jihadi groups, and it took the production of its media to a higher level than any other jihadi group had previously created,” said Laith Alkhouri, a senior analyst at Flashpoint Global Partners, a New York security consulting firm that tracks militant websites. “It literally revolutionized how it produced, distributed and translated its message very quickly. The production value is very high.”