"Instant rumble — and the fireball just went straight up into the sky," is how he describes is.
King was a captain with the Shanksville Fire Department and was one of the first people on the scene when United Flight 93 crashed.
"You didn't see a wing, you didn't see a fuselage," he says. "It's like, 'where is everybody, where are all these people?'"
There was little to see then — and even less to see now. The crash site is surrounded by a chain-link fence and marked with a single American flag. Up on a nearby hill, there's now a temporary memorial, where about 125,000 people come every year. They're not really expecting to see something — they're just hoping to feel something.
"The peace that you feel, the love," says one visitor.
"And just to visualize in your mind what happened," says another.
Hartman says he has no problem visualizing what happened — he was there that day as well, covering the story for CBS News. He hadn't been back since, and was curious to see how the town had changed, five years after the 9/11 attacks.
Except for a few souvenirs in the window, he says, Shanksville is pretty much the same — but the people aren't. They're all coping with the tragedy in a variety of ways.
On one hand, there are people like Judy Brant, who volunteers at the local memorial twice a week.
"A lot of the volunteers feel close to those people," she says of the 9/11 victims. "They died here in our backyard."
On the other hand, there are people like Susan Wilson. When Hartman asked Wilson and her knitting group if any of them had ever been to the crash site, even once, they said no.
"I don't go," she says, raising her hand.
"I didn't want to go there either," another knitter says, "but I had to take my sister once and I was struck — almost by the majesty."
"I don't want to see it. Those are people's families," Wilson says emotionally. "It's sad."
Five years have come and gone, and there's still no right way to feel.
"Let's talk about something else," one of the knitters says.
By the 10th anniversary, there will be a permanent memorial at the site. As you might imagine, the people of Shanksville have very mixed emotions about that. Like the rest of us, they're torn between moving on and the need to never forget.