The White House defended President Joe Biden’s handling of the U.S. withdrawal from Afghanistan on Tuesday, while the Democratic chairmen of three Senate committees said their panels would investigate the rapid collapse of the Afghan government and the Taliban’s subsequent takeover.

Senate Foreign Relations Chairman Bob Menendez said Tuesday that the committee would investigate what he called “shortcomings” in “the Biden administration’s flawed execution of the U.S. withdrawal” and assess why that country’s security forces collapsed so quickly.

“Congress was told repeatedly that the Afghan Defense and Security Forces were up to the task, that it had the troops, equipment and willingness to fight,” the New Jersey Democrat said. “To see this army dissolve so quickly after billions of dollars in U.S. support is astounding.”

Scenes of chaos emerged from Kabul’s Hamid Karzai International Airport on Monday, as Afghans ran alongside and climbed on top of American military planes in desperate attempts to flee the incoming Taliban militants who had taken Kabul hours earlier as Afghan security forces abandoned their posts and surrendered.

White House Press Secretary Jen Psaki, when asked Tuesday about criticism from some congressional Democrats, told reporters that the scenes of the past few days were “gut-wrenching” and “heart-wrenching” but that “these are the difficult choices you have to make as commander in chief, and that’s the choice he made.”

“This happened more rapidly than we, or anyone, anticipated, including those on the ground in Afghanistan and members of Congress,” Psaki said at a press briefing.

“I would reiterate to anyone who’s a critic that any president has to make difficult choices as commander in chief, and the president made the choice that he was not going to ask U.S. men and women to fight a war the Afghans were not ready to fight for themselves,” Psaki said.

White House national security adviser Jake Sullivan told reporters Tuesday that the airport had been secured and the administration is now focused on evacuating U.S. citizens, as well as Afghans who helped during the two-decade-long war.

When such a war ends with an opposing force marching on the capital, “there are going to be scenes of chaos” and people leaving the country, and that “is not something that can be fundamentally avoided,” Sullivan said.

The chairmen have vowed to investigate.

Senate Intelligence Chairman Mark Warner, D-Va., said he hopes to work with other committees “to ask tough but necessary questions about why we weren’t better prepared for a worst-case scenario involving such a swift and total collapse of the Afghan government and security forces.”

Menendez said the Foreign Relations Committee also will “examine the path forward” and focus on crafting an international response to what he called a “looming humanitarian and human rights catastrophe” under the Taliban.

And the top Democrat on the Senate Armed Services Committee, Jack Reed of Rhode Island, said his panel would also bring the issue to the public.

“At the appropriate time, the Senate Armed Services Committee will hold hearings on what went wrong in Afghanistan and lessons learned to avoid repeating those mistakes,” Reed said in a statement.

A broader bipartisan group of 46 senators on Monday asked the Biden administration to grant humanitarian parole to Afghan women who are activists, human rights defenders, parliamentarians, journalists and members of the Female Tactical Platoon of the Afghan Special Security Forces.

The letter to Secretary of State Antony Blinken and Secretary of Homeland Security Alejandro Mayorkas also asked the administration to streamline the immigration process for Afghans seeking to enter the United States.