Aug. 14, 2009 -- For the town of Parkersburg, Iowa, May 25, 2008, started out like any other Sunday.
It was Memorial Day weekend, a day filled with church, family and relaxed celebrations around town. Little did the people of this small town know that just before 5 p.m. they would be faced with a terrifying force that would change their small community, and their lives, forever.
Watch "Blown Away: Twisted Terror" on "20/20" Friday at 10 p.m. ET
Police Chief Chris Luhring, 29, was off duty that day, relaxing with his wife and young children at his in-laws' farm a few miles outside of town.
By early afternoon, the family was outside on the deck, when a storm began to roll in. As the clouds darkened and hail started to fall, the Luhrings admired the power of Mother Nature, unaware of what was about to happen just down the road.
Tyann Lester, then 34, had just finished her morning shift as manager of the Pizza Ranch, a popular hangout located on Highway 57, the main road in town. Her 16-year-old son, Damion, was scheduled to work that afternoon. He quickly dropped her off at home, a few miles from Parkersburg.
As Tyann noticed the clouds darken, she wondered if Damion should skip work and stay home.
But soon her husband called to tell her that a tornado warning had been issued, a common occurrence in this area of the country. "Usually, anytime a tornado warning comes on, nobody thinks anything of it because it never does anything. But it — this day, it just didn't — it didn't feel right," said Lester.
"I thought ... something doesn't feel right. And he looked at me and said, I think it's gonna be a slow night at Pizza Ranch, Mom."
Reluctantly, she let him go.
Meanwhile, just across the street from Pizza Ranch at Matt's Bar and Grill, local football and wrestling champ John Simon, then 17, was setting up for his high school graduation party.
John had decorated the restaurant with his trophies and awards, and was expecting a huge turnout to celebrate his accomplishment.
Tornado Strikes Town as Residents Celebrate Graduation, Memorial Day
"My dad owned a bar and restaurant for 40-some years, and everybody knew us and we knew everybody. So we didn't want to forget anybody," said John. His family even put an ad in the local paper to announce the celebration.
John's girlfriend, Chelsea Poppens, was there to help out. His younger brother Jordan, who was expected at the party, was nowhere to be found.
Everyone gathered was holding out hope that the incoming rain wouldn't ruin the celebration. But as they cheerfully prepared for the party, the dark clouds become impossible to ignore.
They turned on the TV for the latest weather report. It was ominous. "I was like, 'Crap. Nobody's gonna be coming to my graduation,'" said John.
With thunderstorms approaching, storm spotters from nearby police and fire departments were on high alert, surveying the countryside for any possible sign of a tornado.
At about 4:40 p.m., storm spotter Ben McMillan spotted swirling dust formations, an early indication of tornadoes, about 15 miles southwest of Parkersburg. He quickly radioed the National Weather Service, and a warning was issued to Parkersburg and the neighboring counties.
As McMillan turned on his video camera and began to record, an ominous tornado formed above the Iowa cornfields, just miles from Parkersburg.
Click here to watch his eyewitness video of the tornado as it formed.
At 4:51 p.m., the town's sirens began to wail, a signal for everyone to take cover. Local news warned residents to head to their basements, and weather radios all over town blared the alert.
The message was clear: A tornado had stuck ground and was heading straight for Parkersburg, straight for highway 57 and straight for all of the homes and businesses in its path.
Tyann Lester was safe at home, having just sent her son off to work at the Pizza Ranch. Her cell phone rang. It was the restaurant's assistant manager, Jessie Farley.
"And he called to say, Tyann, there's a tornado coming, where do we go? And I was like, you go to the men's bathroom," Lester said. The men's bathroom, built to fit just one person, was the only room at Pizza Ranch that was not against an outside wall.
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While she listened to Jessie hurry the customers inside, Tyann was sure that her son, Damion, could not possibly have made it back to Pizza Ranch in the few minutes since he had dropped her off at home.
"And I make a comment about Damion being late and [Jessie]'s like no, Damion's here, he just got here."
Around town, the citizens of Parkersburg quickly realized that this was not a typical tornado warning. Nor was it a typical tornado that was heading straight for them.
More than a half mile wide, with winds over 200 mph, this was an EF5, the strongest, most dangerous type of tornado on the planet. Storms this strong are extremely rare, but when they do occur, they destroy everything in their path, tearing houses down to the foundation, and sending cars flying hundreds of feet into the air.
As the sirens wailed, John Simon and his family walked outside to see if they could get a better look at the storm, not thinking much of the warning. "They've gone off before, but we just kinda ignore 'em, really," said John.
It was just before 5 p.m., and about 30 people had gathered at Matt's Bar and Grill, ready to start the celebration.
Suddenly, they saw it.
"I looked up in the sky and the clouds went from gray to black, and they're just circling," remembered John. In the chaos, the desperate partygoers split into two groups and ran to take cover. One group, including John's mother, headed for the restaurant's walk-in cooler.
The other group, including John, ran to the car wash next door and frantically tried to get inside. Unable to push in the locked steel doors, they huddled in a walkway between the two car wash bays.
Within moments, the tornado was overhead.
John was terrified. "The whole time I was thinking, Wow, this is really happening. … We're going through a tornado. This is what it's like to die. … I kind of closed my eyes and put my head down, and I was just kind of wishing and praying just, it would just get over with."
In the panic, no one realized that John's younger brother Jordan was neither hiding at the car wash, nor taking cover inside the walk-in cooler.
Mother Listens Over Phone as Son is Caught in Tornado: 'I Let Out a Bloodcurdling Scream, Fell to my Knees'
Meanwhile, at Pizza Ranch, Tyann Lester's son, Damion, and assistant manager Jessie were frantically trying to get the customers to safety, but time was running out.
Lester listened to the commotion over the phone and could hear the boys as they tried to cram everyone into a tiny restroom. Finally, as the tornado approached, Tyann heard Jessie scream, "Here it comes, get down, get down."
Just then, the phone died.
"I let out a bloodcurdling scream, fell to my knees. … And all I could say was, My baby's in there," Lester recalled.
Outside of town, police chief Chris Luhring was unaware that a tornado was bearing down on Parkersbug. In fact, he had made an uncharacteristic mistake. "I'm always ready and prepared. I will tell you that on that day. … I didn't have my pager or my cell phone on me," said Chris.
Suddenly, his in-laws' phone rang.
"My wife's uncle had called and said that his house was in the middle of the street. And in my mind, I'm going, no way, but I'm ready to roll," he said.
Chief Luhring jumped in his truck and sped toward town. At first, the view was reassuring. "I remember coming over the top of the hills, I said, The water tower's still up. The water tower's there."
But what he saw next was beyond all imagination.
"The only thing I could think in my head, this is atomic."
Who lives? Who dies? To find out, watch 20/20 Blown Away: Twisted Terror at Friday at 10 p.m.