Rep. David Schweikert, R-Ariz., said he heard what sounded like “a freight train smashing into a boulder” as a Grand Canyon flash flood consumed the landscape near his rafting group Saturday.

Schweikert told NBC News from his office in Washington on Tuesday that the loud crash was followed by a powerful stream of mud and debris-filled water.

Two visitors died and another is still missing after flash flooding from a sudden deluge of rain briefly transformed Bright Angel Creek into a full-fledged river. About 80 people were evacuated from campsites around the historic Phantom Ranch area of the park.

The retiring member of Congress and the rest of his group were about 100 yards away from the danger zone without cellphone service. His guide led the group to an area off the Colorado River near Bright Angel Creek.

They later left the area on foot — traveling on higher ground — and camped for the night nearby.

It is “monsoon season” in Arizona, but Schweikert said there was not more than a drizzle of precipitation where he was when the dangerous flood ripped through, underscoring the potential randomness of such events.

“At some point, you realized this is a big deal; something’s really gone haywire. … It was a ginormous flash flood,” he said.

The intricate terrain of the Grand Canyon can invite the type of deadly flood conditions that hit the southern part of the national park over the weekend.

“The deluge downpour could have been miles away and was channeled into the canyon, and what used to be a creek now is a river,” said Schweikert, who is a regular Grand Canyon hiker.

The water supply system for the park was also severely damaged, along with part of a new $208 million water pipeline project that was underway near the ranch.