Vice President Mike Pence was moved to tears during a 9/11 memorial ceremony Monday to honor the 40 passengers and crew members who died aboard Flight 93, a plane that was believed to have been headed for the U.S. Capitol after hijackers took control.

"It was the longest 12 minutes of my life, then it turned to 13 minutes, then 14. And then we were informed that the plane had gone down in a field in Pennsylvania," Pence said Monday at the site of the crash in Shanksville, Pa., where a memorial now stands.

Pence was serving his first term in Congress when terrorists hijacked four planes on 9/11 and carried out attacks on the World Trade Center and the Pentagon. He was at the U.S. Capitol that day, which officials suspect was the target of the fourth plane, United Airlines Flight 93.

The vice president said the heroic actions of innocent passengers onboard the plane, who stormed the cockpit in an attempt to wrestle control from the hijackers, is "a debt I don't think I will ever be able to repay."

"I was standing near the East Wing of the House of Representatives," Pence recalled. "I will always believe that I, and many others in our nation's capital, were able to get home that day to hug our families because of the courage and selflessness of the heroes of Flight 93."

"The American people will forever be inspired by their courage and resolve," he said. "We honor them by remembering them… and by doing everything in our power as a nation to prevent such evil from ever reaching our shores again."