Standing in the vicinity of where a plane–full of innocent people who were the victims of one of four terrorist hijackings on 9/11/2001–was forced to plunge into a field in Pennsylvania, Vice President Mike Pence recalled how the heroic actions of passengers likely saved his life.

Pence addressed the relatives and friends of the victims of United Flight 93 attending the 16th-anniversary ceremony on Monday, recalling how he was in Washington as a member of Congress on 9/11, and that when he learned the Capitol was a possible target of the hijacked plane, it was only 12 minutes away.

The somber service began, as it has for the past fifteen years, at 9:45 a.m., which is the exact same time that federal investigators have determined Flight 93’s courageous passengers decided to revolt against their four al-Qaeda hijackers, who ended up crashing the plane into a nondescript field located 60 miles (100 kilometers) southeast of Pittsburgh.

Back in 2001, Pence hadn’t yet finished his first year as a House member from Indiana on the morning when planes hit the World Trade Center and the Pentagon.

The Capitol building and nearby House and Senate office buildings were hemorrhaging lawmakers and aides, Pence recalled, as people ran in every direction, not knowing if they would be the next to be attacked. He ended up with congressional leaders in the office of the Capitol police chief. The room became silent as the chief told those gathered that there was a plane inbound for the Capitol. It was 12 minutes away.

“It was the longest 12 minutes of my life,” Pence said. “But it turned to 13 minutes, then 14, and then we were informed that the plane had gone done in a field in Pennsylvania.”

All thirty-three passengers and seven crew members on the flight, which originated from Newark, New Jersey, and was headed towards San Francisco, were killed.

“Without regard to personal safety, they rushed forward to save lives,” Pence told the people assembled at what is now National Park land. The Flight 93 Memorial features an interactive visitor’s center, which explains in incredible detail exactly what happened to Americans during the worst terrorist act ever to be committed on U.S. soil.

With his wife, Karen, sitting behind him as he spoke, the vice president got choked up. “I will always believe that I, and many others in our nation’s capital, were able to go home that day to hug our families because of the courage and selflessness of the heroes of Flight 93.”

He called the efforts by the 40 crew members and passengers who revolted against the terrorist hijackers “a debt I don’t think I’ll ever be able to repay.”

Roughly 1,000 spectators, including dignitaries and the victims’ friends and families, gathered on a morning that resembled that horrible morning 16 years ago — it was breezy, cool and cloudless on that day, too. In keeping with what has become a long tradition in Shanksville, bells were tolled and the victims’ names were read, one by one. Pennsylvania Gov. Tom Wolf, a Democrat, and U.S. Interior Secretary Ryan Zinke gave speeches before Pence made his remarks.

The $46 million effort to transform the rural Pennsylvania crash site into a national memorial park is nearly complete, after taking many years to get underway.

Ground was broken on Sunday for the final attraction of the Flight 93 National Memorial, which will be a 93-foot (28.4-meter) tall Tower of Voices. The tower, which is going to be built near the park’s entrance, will feature 40 tubular metal wind chimes; one each for the victims.

Bill Adderly, the father of flight attendant CeeCee Ross Lyles, said the Tower of Voices is a fitting way to cap off the memorial site.

“We were here two days after the crash, and never in our imagination did we believe it would be this beautiful,” said Adderly, who lives in Fort Pierce, Florida.

Adderly and his wife, Shirley, were among the family and friends of the victims who were present for Sunday’s tower groundbreaking. At the ceremony, officials played a simulation of what the 40 tubular chimes will sound like when the wind blows through them at the mountaintop memorial.

“The bells, the ringing, I could hear our daughter’s voice in it. She loved to sing. She loved to praise the Lord,” said Adderly.

Actual construction on the tower will begin later this month. Park officials say that the attraction should be completed in time to dedicate the tower for the 17th-anniversary ceremony next year.