President Biden's gut reaction to the news that a deadly suicide bomb had gone off amid the American evacuation from Afghanistan has been revealed. 

During an Afghanistan briefing on Aug.
26, head of US Central Command Gen. Frank McKenzie turned ashen as he was handed a piece of paper. He told the meeting, which he'd called into by video, that a bomb had been detonated near the Hamid Karzai Airport - four services members were already dead, three near dead, dozens more injured. 

There were gasps throughout the room and Biden winced before going silent for a long pause.

'The worst that can happen has happened,' the president said once he broke the silence, meeting participants told the New York Times. 

The death toll eventually rose to 13 US service members and over 170 Afghans. 

The fateful event has since marred the Biden administration's record and defined the frenzied withdrawal that has scored criticism from both sides.

Following the attack, which terror group ISIS-K later claimed, the US carried out a retaliatory drone strike, which they initially claimed killed a terrorist but later admitted had killed an innocent family of 10, including children. 

The president had insisted on pressing forward with the withdrawal of the remaining 2,500 troops in Afghanistan and putting an end to the 20-year war.

Later, as criticism rolled in, Biden laid blame on the Trump-era peace deal with the Taliban, where his successor had promised to have troops out by May. 

On Aug. 31, Biden defiantly dubbed the withdrawal an 'extraordinary success.'