A spokesman for Steven Sotloff's family told CNN the journalist was captured by "so-called moderate rebels" in Syria then sold to the Islamic State in Iraq and Syria (ISIS).
Barak Barfi, identified as a spokesman for the family, said Monday night that sources on the ground have told the family the journalist was kidnapped shortly after entering Syria in 2013 at a fake checkpoint then was sold to the terrorist group for "between $25,000 and $50,000."
Sotloff was killed in a video released by ISIS last week. He was the second U.S. journalist beheaded by the terrorist group.
Some lawmakers have called on the United States to increase its support to vetted rebel groups in Syria as part of a broader plan to combat ISIS.
Barfi was a friend of Sotloff, who talked with him shortly before he was kidnapped. He is currently a research fellow at the New America Foundation.
He said the relationship between the family and the Obama administration is “strained.” He accused the government of making a number of inaccurate statements.
"They've said that the families have been consistently and regularly informed," he said. "That is not true. I speak now only from the Sotloff family. I can't speak for the other families."
He said the family does not believe the U.S. government gave it the cooperation it needed. He said the family made a request to the government that was rebuffed after ISIS released the first video threatening Sotloff's life.
Barfi said he could not detail the request.
"I can't say that because I have to think about protecting the other hostages inside," he said.
Last month, Sotloff's mother made a plea for her son’s life in a video released to media.
Shirley Sotloff had appealed directly to Abu Bakr al-Baghdadi, the leader, asking him to show mercy on her son.