Changes to a drive control system and rapid speed changes made by an operator led a Texas mother and her two young girls to be thrown about 25 feet off a Ski Granby Ranch chairlift in December 2016, state investigators said in a final report on the incident.

The 40-year-old woman — Kelly Huber — was killed and her two children hurt in what the report said was an “unprecedented” sequence of events that none of those who reviewed the case had ever seen before.

“No one on the investigative team has ever witnessed or heard of a similar event,” said the 151-page report, released Thursday afternoon. “Likewise, literature does not describe such an event.”

The Colorado Passenger Tramway Safety Board report, released more than four months after the fatal fall, squarely places blame for the incident on a lift malfunction and ends speculation about an incident that gripped the ski industry. Huber’s death was the first related to a lift malfunction in the U.S. since 1993 and the first death from a chairlift fall in Colorado since 2002.

Read the full story on The Denver Post website.