McGuire identified the residents of the home Friday morning as Maureen Morris, 65, and Jeff Elsey, 58.
Springdale and Zion Canyon Police Chief Kurt Wright said two bodies had been located amid the rubble. According to Wright, the boulders that struck the home which probably weighed several hundred tons would have come down so quickly that the victims were likely killed instantly.
One boulder will have to be removed in order to recover the bodies, Wright added. Crews were evaluating how to move the massive rocks, and Wright said the process will likely take all of Friday.
"Our concern is finding something big enough to move the boulder," he said.
Alex Gardner left his home on the Anasazi Mesa above Rockville around 5 p.m., driving to a meeting in Cedar City. As he neared Rockville, "I saw a huge cloud of dust."
Gardner realized he left something in his house, so he turned around.
"As I turned around, emergency crews passed me coming out of Springdale," he said.
When he returned, "the cloud of dust was even bigger."
McGuire said the town has seen slides in the past, including one that took out part of a home more than a decade ago. However, Thursday's slide was the biggest and most devastating in recent memory.
Gardner stopped at the site of the rock slide and took photographs of the destruction. He said several large boulders had come down.
Wright blamed the slide on unusually low temperatures and heavy snowfall. He said the area is experiencing the coldest weather in 27 years, and as much snow as the town has had in a century. But on Thursday, temperatures peaked at about 45 degrees, which Wright speculated thawed the frozen rocks and sent them rolling down the hill.
The process of moving the rocks and retrieving the bodies was called off Thursday night and will resume Friday at 8 a.m. Residents of the area are free to return to their homes, though Wright said authorities don't know if more slides are imminent.
Those wishing to evacuate their Rockville homes have been offered free lodging in nearby Springdale, Wright added.