Twin bombings at the gates of Kabul’s international airport and a nearby hotel killed 10 U.S. Marines, two soldiers, one Navy corpsman and dozens of Afghan civilians Thursday, throwing the final days of a U.S.-led evacuation effort into chaos and fulfilling a nightmare scenario President Biden’s top aides had desperately sought to avoid.

The explosions, which also wounded 18 Americans and scores of Afghans, came as the United States and other Western nations rushed to complete the evacuation of tens of thousands of citizens and Afghan allies ahead of an Aug. 31 deadline.

President Biden vowed to punish the assailants but said the United States would continue running evacuation flights to bring Americans and Afghan allies home.

“We will hunt you down and make you pay,” Biden said before taking a moment of silence for those killed in the assault, the deadliest attack on U.S. forces in Afghanistan since 2011.