text:  The panel's Republican chairman, James Comer, says Americans are demanding answers from Cheadle about what Comer calls the historic security failures at the rally that day. That includes how a gunman was able to get onto a roof with a clear line of sight on the former president. Questions also have been raised after it emerged that the Secret Service knew about a threat before Trump took the stage that day but still allowed him to go out and speak. Ryan Lucas, NPR News, Washington.