With the Taliban growing more violent and adding checkpoints near Kabul’s airport, an all-volunteer group of American veterans of the Afghan war launched a final daring mission on Wednesday night dubbed the “Pineapple Express” to shepherd hundreds of at-risk Afghan elite forces and their families to safety, members of the group told ABC News.

Moving after nightfall in near-pitch black darkness and extremely dangerous conditions, the group said it worked unofficially in tandem with the United States military and U.S. embassy to move people, sometimes one person at a time, or in pairs, but rarely more than a small bunch, inside the wire of the U.S. military-controlled side of Hamid Karzai International Airport.

The Pineapple Express’ mission was underway Thursday when the attack occurred in Kabul. Two suicide bombers believed to have been ISIS fighters killed at least 13 U.S. service members — 10 U.S. Marines, a Navy corpsman and an Army soldier and one to be determined — and wounded 15 other service members, according to U.S. officials…

As of Thursday morning, the group said it had brought as many as 500 Afghan special operators, assets and enablers and their families into the airport in Kabul overnight, handing them each over to the protective custody of the U.S. military.