Scot Denhalter stands beside the giant 12-foot-wide-by-9-foot-tall boulder that pummeled into his home on Jan. 21 in St. George, UT. Image credit: Scot Denhalter

It was a nightmare for a Utah woman who awoke in the middle of the night to the rumble of a boulder that rammed through her bedroom.

The 12-foot-wide-by-9-foot-tall rock pummeled through Wanda Lee Denhalter's bedroom at 3 a.m. Jan. 19, breaking her jaw and sternum.

Her husband, Scot Denhalter, was not home during the incident.

"Just knowing a rock had pinned her in the bedroom frightened me," Denhalter was quoted as saying in The Spectrum. "I feel a bit guilty because I wasn't there. She stumbled around probably in shock. She found her phone and called 911."

Wanda Lee Denhalter, 63, was taken to a hospital for surgery, according to The Salt Lake Tribune. "She was treated and released," said Terri Draper, a spokeswoman for Dixie Regional Medical Center.

"I guess she heard the rumbling as it came down the hill and woke up," Scot Denhalter was quoted as saying in The Salt Lake Tribune. "She rolled away from the oncoming noise to my side of the bed. If she had decided to swing her legs over the side of the bed and get up to investigate, it would have killed her."

ABC News was unable to reach the couple.

The Denhalters moved into the rental house in mid-December, according to The Spectrum. Scot Denhalter's concern at the time of their move was that the rocks were sitting atop a ridge overlooking their home.