A typical Nusra video, Zelin said, “would start out with a graphic of the media outlet, then a Quranic verse written out, then a series of videos of attacks or someone reading his last words before going out on a suicide mission, a martyrdom operation.”

McCants, the former government terrorism adviser, echoed that observation.

“Everything about the video is uncharacteristic of a polished al Qaida group like Nusra,” he said. “It doesn’t mean it wasn’t them, but there’s nothing that points in that direction.”

Tice, a former infantry officer in the Marine Corps, entered Syria in May, crossing into rebel-controlled territory via Turkey and traveling in and around Damascus since late July. He contributed more than a dozen articles to McClatchy and three to The Washington Post, with his own military experience adding nuance and detail to dispatches from the front lines of the civil war. He also freelanced for CBS News, Al Jazeera English and the Agence France-Presse news agency.

Since Tice’s disappearance, information has emerged from both official and unofficial sources to suggest that government authorities captured him. References to him in pro-regime social media outlets as well as press mentions in Iran, a close ally of the Syrian regime, paint him as a spy.

A Facebook page in the name of Assad, the Syrian president, includes a Sept. 16 entry that referred to Tice as an Israeli agent who’d “infiltrated” the country. An Iranian news portal claimed that Tice was a CIA agent who faces the death penalty after being captured by the Syrian military and held in connection with killing three air force officers. The Syrian government has denied any knowledge of Tice’s whereabouts.

The Committee to Protect Journalists has documented a resurgence in dangers faced by journalists in Syria over the past six weeks, noting Tice’s case as well as the disappearance of two other foreign journalists – Turkish cameraman Cuneyt Unal and reporter Bashar Fahmi, a Jordanian of Palestinian origin – who work for the U.S. government-funded Al Hurra TV channel.

“We are deeply concerned about the fate and safety of U.S. freelance journalist Austin Tice and call upon his captors to disclose his whereabouts and release him immediately,” Robert Mahoney, the committee’s deputy director, said in a statement.