A storm chaser from Regina who spent the night in an area of Arkansas that has been devastated by a killer tornado says it was as if "an atomic bomb" had gone off.

Greg Johnson and Ricky Forbes, who is also from Saskatchewan, headed to the area last week and were near the town of Vilonia on Sunday night when the deadly tornado struck. At least 16 people were killed.

"It was an incredible and tragic experience," Johnson said. "It looked like an atomic bomb went off."

Johnson, a photographer and writer who creates books about his storm-chasing experiences, said his team immediately went into first-responder mode, trying to help people emerging from their ruined homes.

'It was an incredible and tragic experience … it looked like an atomic bomb went off.' - Regina storm chaser Greg Johnson

He told CBC Morning Edition host Sheila Coles that he parked in a residential area where he saw a steady stream of people walking away from their ruined homes. Some people apparently had broken limbs, while others were impaled by pieces of debris.

"It was an unbelievable, surreal experience," Johnson said. "Definitely a worst-case scenario on these small communities."

Johnson said among the people he helped was a father of three young girls who had a cut arm that needed treatment.

The man told him that his house had been destroyed. He and his girls hid in a bathtub and somehow survived as things fell to pieces all around them.

When the tornado had passed, the bathtub was about 30 metres away from where the house had been, Johnson said.