An emotional interview this morning on America's Newsroom as Bill Hemmer sat down with the mother of a U.S. soldier who is said to have been killed while searching for Army Sgt. Bowe Bergdahl in Sept. 2009.

The Obama administration has pushed back against claims from former soldiers that at least six of their fellow service members were killed while searching for Bergdahl.

Cheryl Brandes said she has spoken to the six platoon mates of Bergdahl, who appeared together on The Kelly File last night, and has no doubt they are telling the truth. She says they have told her that her son, 20-year-old Pfc. Matthew Martinek, was part of a search for Bergdahl when he was struck by an IED a few months after Bergdahl walked off the base.

"The accounts of everything that happened, every detail that I was told when my son was hit. There's no way that anybody could ever make anything like that up. They wouldn't do that. They're not liars. They're our defenders of America," said Brandes.

Hemmer then asked for Brandes' response to Defense Secretary Chuck Hagel, who said Wednesday that he doesn't know of any "specific circumstances" of soldiers being killed while searching for Bergdahl.

Directing her answer at Hagel, she said, "You weren't there to see those boys witness that. You weren't there. You can't tell me that."

Brandes is demanding an investigation into the matter, but doubts that will even lead to the truth for the families of fallen soldiers.

"Why were we not told the truth? Why is this such a cover-up?" Brandes asked, wondering "what is so bad" about admitting that soldiers died looking for another soldier.

"There's nothing bad about that. We just want the truth."

Brandes said she sympathizes with Bergdahl's parents, but wants them to understand what she and other families are going through.

"His mom, I'm sure that she wants her son back. I want my son back too. I get a picture, you get a human," she said.

Watch the full interview above, plus tune in for part 2 of Megyn Kelly's sit-down with Bergdahl's platoon mates, tonight at 9p/12a ET.