WASHINGTON (CNN) -- Late on the night of last September 11th, U.S. Ambassador to Libya Christopher Stevens spoke to his deputy for the final time from the diplomatic compound in Benghazi, Libya.
"Greg, we're under attack," Stevens told Gregory Hicks.
Within hours, Stevens and three other Americans were dead, victims of an armed terrorist assault that has since become a political and foreign policy flashpoint in Washington's partisan wars.
The dramatic narrative recounted by Hicks at a six-hour Republican-led House hearing on Wednesday reflected the knowledge of a high-level insider who was in Libya that long night and was deeply involved in trying to react to events.
His efforts to determine the circumstances of the attack and muster help for those under siege in eastern Libya were later praised by his superiors and by President Barack Obama.
The step-by-step account riveted the Republican-led Oversight Committee proceeding that was also marked by sharp partisan exchanges over the merits of continued congressional inquiries over the attack.
Republicans once again accused the Obama administration of trying to cover up the fact that it was a well-orchestrated assault by militants, failing to adequately explain events to the public, and then refusing to cooperate with congressional investigators.
Democrats once again accused Republicans of using tragedy for political gain.
Hicks -- praised by Republicans as a "whistleblower" -- was joined at the witness table by Eric Nordstrom, a former regional security officer in Libya, and Mark Thompson, the State Department's acting deputy assistant secretary for counterterrorism.
Our goal "is to get answers, declared committee chairman Rep. Darrell Issa, R-California. "The administration, however, has not been cooperative."
Hicks described in personal detail how he missed Stevens' initial call and then reached him by cell phone as the attack unfolded in phases.
"I got the ambassador on the other end and he said, 'Greg, we're under attack.'"
He recounted the efforts of a security response team on site that drove back the attackers, and "repeated attempts" by those on the ground to enter the burning compound to try and rescue Stevens and others.
He then said that Stevens was at a hospital that was controlled by a group that he said Twitter feeds identified as leading the attack. Was it a trap to lure more Americans? Then the worst news about his boss.
"I received a call from the prime minister of Libya. I think it's the saddest phone call I've ever had in my life. He told me that Ambassador Stevens had passed away," Hicks said.
Oversight committee Republicans continued to go after televised remarks by U.N. Ambassador Susan Rice five days after the attack. In them, she insisted it was the result of a spontaneous demonstration over an anti-Islam film that turned violent.
GOP critics believe Rice was shielding Obama at the height of his re-election campaign during which there were times that he trumpeted U.S. successes in combating terrorism, including the death of al Qaeda leader Osama bin Laden in 2011.
Administration officials say Rice was using official talking points that relied on the best available information at the time. Rep. Patrick McHenry, R-North Carolina, asked Hicks if there was any evidence early on that the attack was a protest.
"No, there was none," Hicks said. "I'm confident Ambassador Stevens would have reported a protest immediately if one appeared on his door."