The Boulder County Sheriff's office said he was performing off-season trail maintenance Thursday morning when it happened. Ski patrol began CPR on the man immediately and called a flight for life helicopter, but the man died before it arrived. It's not clear what caused the tree to fall on the employee. More local videos here: https://youtube.com/@9news Subscribe to NEXT: https://youtube.com/@Nexton9NEWS Stay connected: 9NEWS Website: https://www.9news.com/ Facebook: https://www.facebook.com/ilike9news Twitter: https://twitter.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.