FORT KNOX, Kentucky -- Fort Knox Firefighter Glen Robinson tolls a bell in sets of five, a firefighter tradition, to honor lost lives during a Patriot Day ceremony Sept. 11, 2017 at Fort Knox Fire Station No. 1, as Lt. Chris Evans, left, and Firefigh...

FORT KNOX, Kentucky -- (from left) Maj. Gen. Donnie Walker Jr., Lt. Col. Ed Otalora, Military Police Sgt. Liza Ascue, and Firefighter James Gambino salute after placing a wreath at a 9/11 memorial featuring a section of beam from the World Trade Cent...

Maj. Gen. Donnie Walker Jr. was not surprised people across the United States felt the pain caused by the Sept. 11 attacks.

"We're united by a common spirit," he said.

Walker, commanding general of the 1st Sustainment Command, addressed a crowd Monday in front of Fort Knox Fire Station No. 1 who gathered for the annual Patriot Day ceremony to remember the events of Sept. 11. Monday marked the 16th anniversary of the attacks.

"(It's) a day when we remember those who lost their lives and reflect on the power of the American spirit," he said.

Walker recounted the events of Sept. 11, from the two planes striking the two towers of the World Trade Center and their collapse an hour later to the crash of United Flight 93 near Shanksville, Pennsylvania, and American Airlines Flight 77 crashing into the Pentagon.

Walker was assigned to the Pentagon that day. He said sheer panic grabbed the Washington, D.C., community.

"It was one of the most bizarre and incredible experiences to see the Beltway shut down and people walking on the I-395," he said. "It was equally amazing to witness strangers pulling together for a common good so quickly."

He said the attacks fused uncertainty into society, but instead of turning toward fear, Americans became more vigilant, more unified and more committed.

"The American spirit is undeniable," he said.

Monday's ceremony featured a 21-gun salute, playing of taps and a memorial tolling of the bell to honor victims.

Stephen Snider, assistant chief of the Fort Knox Fire Department, said he hoped the remembrance and recognition of all heroes will inspire a sense of dedication.

"It's the love of freedom that binds us," he said.

The bell was struck five times each for those who lost their lives at the World Trade Center, the Pentagon, on Flight 93 and for the 343 firefighters who died.

Each year, ceremony officials try to involve a local department in the ceremony, said Todd Vinton, assistant chief in Fort Knox Fire Department's training division.

This year, the fire department from Flaherty provided a ladder truck to help hold the American flag.

Vinton said the ceremony helps those remember.

"You'd be surprised at how many people don't talk about what happened," he said. "We're getting to where we are forgetting."

During his address, Walker took time to acknowledge the sacrifices of first responders.

"To the policemen who ran into the tower and firefighters who stepped into the smoke ... thank you for coming to our aid," he said.

He asked audience members to always remember those who ran into danger to save lives.

"May God continue to bless our Armed Forces, first responders and their Families," he said at the end of his speech. "May God bless those innocent Americans who just got up to go to work that day."