It's been nearly 16 years and Herb Penner still can't believe the tragic events of Sept. 11, 2001.

"I can't, I just can't imagine it; still to this day," the retired firefighter said as he stood in front of the 9/11 Never Forget mobile exhibit at the Douglas County Fair. The emotions of that day can still be seen is his eyes and heard in his voice.

The exhibit, which opened Thursday at the fair is free to all fair visitors. Penner is one of the guides for the exhibit, that is housed in a semi-trailer and travels the country.

Penner, who retired in 2011, was a New York City firefighter for 30 years. He was on duty the day the Twin Towers crumbled to the ground after being struck by two planes in a terroristic attack.

He heard the first plane flying overhead while he was in Manhattan, which he said was odd because people never heard planes in that area. A call came over the radio that said the first tower had been hit and at first, he thought it was someone goofing around.

Until, he said, an all-call page came over urgently requesting all firefighters to report for duty, even if they were not on-call that day.

At that time, Penner said he was a fire department captain in the Bronx. He had lived in New York his whole life and grew up in Queens. After the attack, his wife, Betty, didn't know what happened to him. She didn't know if he was alive or dead.

"I finally came home on the third day," he said, shaking his head. "She didn't know where I was for three days."

Penner said that his department was put on a city bus that day and they were all brought to the scene together.

Thinking about it and talking about it still makes the hair on the back of his neck stand up, just like it did that day, he said.

But talking about the tragedy and being able to show people just a small glimpse of what happened nearly 16 years ago when they visit the traveling exhibit is therapeutic for Penner. And it has become easier as time goes on. He said the first time he saw the 9/11 Never Forget mobile exhibit, he just stood in the corner and didn't really talk or look closely at the pictures and pieces that were left behind to become memorials.

He has also never been back to what has now become known as Ground Zero. He said he has never went to the memorial or read the names on the wall. It's too hard, he said.

"There are bodies still missing," he said. "But we did the best we could."

Penner said he will never forget that day. And then he jokingly said he should have picked a different career, like a banker, as he didn't know his son, Mike, would follow in his footsteps. But with a grin, radiating from ear to ear, he said Mike is currently a firefighter with the New York City Fire Department.