"She told me at the last second when the boulders were coming down on top of them that he covered her up and protected her, which I believe it saved her life," said sheriff's Deputy Nick Tolsma.
Gracie's parents and sister from nearby Buena Vista were killed, as were two of her cousins from Missouri.
The sheriff's department identified the dead as Dwayne Johnson, 46, and Dawna Johnson, 45, Gracie's parents; and her 18-year-old sister, Kiowa-Rain Johnson.
The other victims were identified as Baigen Walker, 10, and Paris Walkup, 22, both of Birch Tree, Mo. They were nephews of Dwayne and Dawna Johnson.
All five bodies were recovered Tuesday afternoon and identified by a family member, Sheriff Pete Palmer said. Palmer said the coroner will make the final, formal identification.
Dwayne and Dawna Johnson were coaches in Buena Vista schools, were well known in the town and very active in community events, the sheriff's department said.
Family friend Mike Carr of Buena Vista said Dwayne Johnson was quick to help others.
"Probably his only regret is that he didn't jump in front of his whole family. He's just that type of guy," Carr said. "He probably did that without one bit of hesitation."
Monday's slide sent 100-ton boulders onto a popular viewing area that overlooks Agnes Vaille falls below 14,197-foot Mount Princeton in south-central Colorado.
The massive slide left a gash the size of a football field in the mountainside, Undersheriff John Spezze said.
What triggered it wasn't immediately known, though Spezze said the area had heavy summer rain and a recent snowfall.
Rain or melting snow can make slides more likely by weakening a steep slope and making the rocks and soil heavier, said Jerry Higgins, an associate professor of geological engineering at the Colorado School of Mines in Golden.
With enough data, geologists can identify slopes that are susceptible to slides, Higgins said, but finding all of them would be a massive undertaking.
"In Colorado, there's a lot of steep slopes, and I don't think anybody's got the money to pay for the studies for all the steep slopes," he said.
Witnesses said some of the boulders were the size of cars. A hiker who heard the slide in Chalk Creek Canyon ran down the trail and called for help, Spezze said.
Tolsma said he was one of the first at the scene and heard screaming from beneath the rubble. He saw Gracie Johnson's hand sticking up through the rocks.
"I started digging her out until I had more help come and we got her all the way out," he said.
The rock slide was too unstable for crews to retrieve the bodies Monday, so they waited till Tuesday, authorities said.
The U.S. Forest Service maintains the busy trail near St. Elmo ghost town. Spezze said officials have asked the Forest Service to close it permanently.
The trail is one of the first hikes recommended to people new to the area and is popular with tourists, said Margaret Dean, a regular hiker who has walked the trail with her 7-year-old grandson.
Dean, a copy assistant at The Mountain Mail newspaper in Salida, said the trail provides a view of the falls and the Chalk Creek Valley in the towering Collegiate Peaks.