Transcript for Activists Report Drone Over ISIS Stronghold
Joan rivers, tonight at 10:00 P.M., 9 central, right here. And you're about to see what could be a U.S. Drone flying over a key drone in Syria. Ryan Ross, with the image of that drone and the new scrutiny tonight. An American from Michigan, are his videos inspiring some to join the enemy? Reporter: Today, over the Isis stronghold of raqqah, Syria, a sign of the battle that could be coming. Activists in Syria posted this photo of what they said was an unarmed U.S. Drone. Isis posted its own photos of the surveillance craft circling the city. The U.S. Is urgently seeking intelligence on potential military targets and on any sign of the two American hostages still held by Isis. Where are they? And are there any rescue attempts that are possible? Reporter: The U.S. Is also searching for some other Americans in Syria, those like this former college student from Boston, who have turned on their country to join Isis. The jihadist recruitment pipeline to Syria from the U.S. And Europe is of huge concern to law enforcement authorities. Why did this happen to us? Reporter: And now, they are closely monitoring the preaching of this charismatic Muslim cleric now living in Dearborn, Michigan, Ahmad jibril. I want you to know that these were real men who were there to give their jugular veins for the sake of Allah. Reporter: Jibril's internet videos are credited with inspiring an estimated 60% of the western recruits in Syria according to a study done at kings college in London. They were regularly listening to his sermons, and they were clearly influenced by him. Reporter: Jibril, who spent five years in prison on federal fraud charges, does not specifically urge his followers to violence, but says the U.S. Wants muslims to die. They are waiting for the maximum amount of Sunni deaths, yes. To pleasure and delight their hearts. He is feeding the narrative without making an open call to violence, and then when it's time to convince them to fight, you're already halfway there. Reporter: We tried to find jibril at a relative's home in Dearborn, Michigan, but no one would come out to talk with us. His lawyer said she had no comment. Thank you. And tonight, there's a developing news headline about another top terrorist.
This transcript has been automatically generated and may not be 100% accurate.