Federal investigators are seeking help to identify a masked man they believe may be an American who's appeared in a propaganda video on behalf of the terror group the Islamic State of Iraq and Syria, or ISIS.

Shifting between Arabic and English, he has orchestrated the execution of prisoners last month in Syria, CBS News' David Martin reports.

The FBI posted a clip on its Web site in the hope someone might recognize him through his voice and appearance.

Judging by his accent, the FBI believes he is from the northern U.S. border area with Canada or from Canada itself.

He is not the first ISIS fighter to be hunted by the sound of his voice.

"Jihad John," the terrorist who presided over the execution of Americans James Foley and Steven Sotloff, spoke in a British accent. Following that lead, law enforcement officials said they have succeeded in identifying him.

ISIS fighters holding Western passports are considered a threat to return home and carry out terrorist attacks in Europe or the U.S.

That's why the FBI is appealing to the public to "help identify individuals traveling overseas for combat."

Chilling videos featuring English-speaking fighters are actually used by ISIS to recruit more fighters.

Over the weekend, a 19-year-old Chicago man was arrested for allegedly attempting to travel to Syria to join ISIS.

The FBI appeal includes a tip line, 1-800-CALL-FBI, and a Web address citizens can use to help identify ISIS fighters.

"No piece of information is too small," the FBI said.