Gov. Mark Dayton has ordered all U.S. and Minnesota flags to be flown at half-staff on state property to mark the 10th anniversary of the Sept. 11 terrorist attacks.

Dayton, who was U.S. Senator at the time, also offered his remembrance of the attacks while living in Washington.

He said when he returned to the hotel where he was living, the general manager invited him to the roof of the building.

"As we stood there, twelve stories above the ground, Washington was strangely quiet," he said in a statement. "There was not a cloud, plane, or helicopter to be seen anywhere. The clear blue sky was, however, rapidly being filled by a mushroom cloud of thick, black smoke pouring from the Pentagon."

Dayton said he couldn't believe it was really happening.

"Everything happening was so incredible that I must be dreaming," he said. "At the same time, however, I knew this terrible nightmare was all too real. I have prayed many times that that I will never experience it again. I pray that our country will never experience it again."

That night, Dayton recalled, he joined other members of Congress on the steps of the Capitol. Dayton remembered that as the speeches ended, they began singing "God Bless America."

"I still get shivers, whenever I hear that song," he said. "It reminds me that, whatever our differences, we all do love our country, and that we are so fortunate to live in the most extraordinary democracy the world has ever known."

Dayton said he learned a valuable lesson after the attacks.

"We are not invulnerable," he said. "A small number of murderous fanatics were able to do that day what no foreign power had accomplished since Pearl Harbor: to attack, kill, and injure thousands of innocent Americans on our own soil."

Dayton said that military force is not the only answer, we must also work with other nations to ensure peace.

"We need friends and allies everywhere, who will alert us when they become aware of suspicious terrorist activities; rather than waiting and then cheering after they are inflicted upon us," he said. "We need to be the best leader the world has ever known. A leader that the rest of the world respects, admires, and wishes to befriend. Therein lies our security … and theirs."