A report detailing what went wrong during a deadly avalanche in the sierra this past winter was released on Sunday. The Feb. 17 avalanche near "Perry Peak" in the Truckee area killed nine people, and sparked questions about why the group left their ski huts in a snowstorm, with active avalanche warnings. Watch NBC Bay Area News free wherever you are WATCH HERE WATCH HEREThe 68-page preliminary report found that the guides decided to leave during a break in the storm, on the last day of what was supposed to be three days of back-country deep-powder skiing. Before going into the path of the avalanche, GPS data shows the group made multiple attempts to avoid the riskiest part of the avalanche zone by crossing a creek that is usually covered in snow, but they were blocked by open water and steep creek banks and were forced to go back to the other exit trail. The report was written by a veteran mountaineer and risk consultant who formerly operated the American Avalanche Institute in Colorado.