Updated at 1:45 p.m. ET: A Utah woman got a startlingly rude awakening at her hillside home over the weekend: a boulder in her bedroom at 3 a.m.

Wanda Denhalter, 63, was home alone on Saturday when the enormous rock crashed into her room, breaking her jaw and sternum, and leaving a huge gash on her leg, The Salt Lake City Tribune reported. Her husband Scot, who was out of town for the night visiting his son, told The Tribune he estimated the boulder that he returned home to was about 12 feet long, 9 feet high, and 9 feet wide.

"I guess she heard the rumbling as it came down the hill and woke up," Scot Denhalter, 62, told The 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."

Somehow, despite her injuries, Wanda Denhalter managed to get help.

"She stumbled around, probably in shock. She found her phone and called 911,” Denhalter told St. George local media source Spectrum.com. "I feel a bit guilty I wasn't there."

The couple just moved into the rental home in St. George in mid-December, local reports said. No one else was hurt when the boulder came loose. It's unclear what caused it to come rolling down the hill in the first place, but Scot Denhalter said a neighbor told him water appeared to be draining from a home on top of the ridge.

“It might have been a pipe that froze and broke," he told Spectrum.com. "It’s been kind of leaking into the fissures and cracks of the ridge, and I think last night when the water froze, it snapped and down it came.”

While police were not able to pinpoint exactly what sent the boulder rolling down the hill, St. George city spokesman Sgt. Marc Mortensen said Tuesday that no further investigation was planned on the incident, which he described as a "natural occurrence." 

"The boulder in the hillside was in its natural state. It evidently broke loose or the soil around it somehow came loose," he said. "In our county and in our city, we have hillsides all over the place. We're very hilly. So this type of occurrence, while not common, it does happen from time to time."

Usually, though, people aren't injured because the boulders are significantly smaller. Police are not concerned about more boulders falling in the area, he added.

Wanda Denhalter has been released from the hospital and is recovering from her injuries, he said.

"What a wake-up call!" Mortensen said of her 3 a.m. ordeal.

Scot Denhalter said he was relieved his wife was alright.

“When we first moved in, my wife said, ‘Don’t you love the backyard?,’ and I did because of the position of the ridge,” he told Spectrum.com. “[But] I said you could have a big boulder snap and come down and come right through the house, but she said that would never happen.”

“I’m greatly relieved she’s OK,” he said.

St. George is a desert community in the southwest corner of Utah, on the border of Arizona.