Why is a general who helped cover up the friendly-fire killing of an American hero being appointed to lead a presidential commission on military families?

That's what the mother of Pat Tillman wants to know, and she's calling on President Obama to reverse the selection.

“Considering that we have plenty of evidence indicating that McChrystal was involved in the cover-up of Pat’s death... he's not the right person for that kind of a job," she told ABC News in an exclusive interview with Jake Tapper.

McChrystal resigned his post as one of America's top military generals after a feature story by Rolling Stone reporter Michael Hastings quoted him mocking the president and other civilian leaders.

This video is from ABC News, broadcast Thursday, April 14, 2011.