BOULDER COUNTY, Colo. (KDVR) – The Boulder County Sheriff’s Office has released a sketch and description of the suspect in an assault that occurred on July 28 at the Walker Ranch Open Space near Martin Gulch.

The suspect is described as a man who is over 6 feet tall with a muscular build. He weighs over 225 pounds and is believed to be in his 40s. He is bald and was wearing a mask during the assault.

The sheriff’s office said the attack occurred near 7701 Flagstaff Rd., about 9 miles west of Boulder.

A woman was hiking alone when she says she was approached by an unknown man who sexually assaulted her.

Any witnesses or people with information are asked to contact Det. Asa Merriam at 303-579-3611 or amerriam@bouldercounty.org.