Man posing as 'husband' tried to free Kayla Mueller from ISIS captivity, US lawmaker says

American Kayla Mueller, 26, was killed while in the hands of ISIS, her family said Tuesday.

Kayla Mueller may have been close to freedom and never known it, after a man believed to be her friend showed up at an ISIS terror camp and identified himself as her husband, only to be sent away when the Arizona aid worker told her captors she wasn't married, according to the Congressman who represents the Mueller family's district.

Arizona Rep. Paul Gosar learned from the family that a man posing as Mueller's husband demanded her release from ISIS but was unsuccessful in his attempt, a Gosar spokesman told FoxNews.com.

The person pretending to be Mueller's husband is believed to be the Syrian man with whom Mueller was captured with in August 2013, according to Gosar spokesman Steven Smith. The man, who has not been named, was released by ISIS days later, while Mueller was transported to a holding cell with other hostages.

At some point, the man posing as the 26-year-old aid worker's husband appeared at the Syrian terrorist camp where she was being detained. But Mueller "had no information" it was a rescue mission and the man was turned away.

"She said she didn’t have a husband," Smith said. "That was all the captors needed to send the person posing as her husband away."

Carl and Marsha Mueller, of Prescott, Ariz., confirmed Tuesday that their daughter was killed while in the hands of ISIS. After the family received a private message over the weekend from her captors, including photos, the intelligence community concluded Mueller was dead.

It remains unclear how and when she died. The Islamic State claimed last week that Mueller was killed in a Jordanian airstrike on a weapons compound in Raqqa, Syria-- a claim both the White House and the Pentagon have denied.

White House Press Secretary Josh Earnest said Tuesday there was no evidence civilians were in the area struck by Jordan in retaliation for the videotaped burning death of one of their pilots, Lt. Muath al-Kaseasbeh.

"What is not possible to call into question is that ISIL, regardless of her cause of death, is responsible for it," Earnest said.

At approximately 3 a.m. on July 4, 2014, U.S. special operations troops launched a hostage rescue attempt in Syria at a jihadist base known by terrorists as the "Usama bin Laden Camp." The troops failed to find the hostages, including Mueller, and were forced to withdraw after a gun battle with ISIS militants, according to the Pentagon.

U.S. intelligence sources said the White House knew of the hostages' exact location eight months ago -- at the end of May 2014 -- but did not sign off on the raid until six weeks later. The reason for the delay is not known.

U.S. officials were unable to confirm reports Wednesday that cited unnamed intelligence sources and claimed Mueller was given as a "bride" to an ISIS fighter while in captivity.