A woman was found unresponsive on a swim beach on Friday afternoon after paddle boarding has passed away, and her dog is still missing.

Dr. Hope Cassel, 45, was taken to the hospital in critical condition after Littleton Fire Rescue responded to the west side of Chatfield Reservoir after 1 p.m. Friday on a report of a near drowning, 9NEWS reports. She passed away Sunday night at 11 p.m.

Dr. Cassel was an OB/GYN and a mother of 3 from Parker. She was paddle boarding with her teenage sons and a friend of the boys when a sudden storm of heavy wind, rain, lightning, thunder, and hail came up, building large waves and throwing the family off their boards.

The 4 boys were wearing life vests and made it to shore. Cassel and her golden retriever, who was on the board with her, did not.

The dog has not yet been found.

It's not clear as to whether Chatfield Reservoir has medical personnel working alongside rangers like they do at Horsetooth Reservoir.

This summer, Larimer County launched a partnership with UCHealth's Poudre Valley Hospital EMS and Poudre Fire Authority to provide medical personnel on weekends and holidays throughout the season on Horsetooth Reservoir to reduce first response time with not only water injuries, but also hiking injuries, snake bites, heat exhaustion, heart attacks, and other major medical issues.

Even so, this is such a tragic accident and our hearts go out to Dr. Hope Cassel, her family and friends, and all the clients whose lives she impacted with her dedicated work in the medical field.