An investigation is underway after a woman was grabbed in broad daylight and sexually assaulted in Fort Collins on Monday afternoon.

Police said the woman was on a walk when a stranger grabbed her from behind and sexually assaulted her just after 3 p.m. in the 1200 block of East Elizabeth Street.

A bystander witnessed the assault and yelled at the perpetrator, which caused him to run away. The bystander then spoke with the victim before leaving to find additional help and contact the police, according to a release from the Fort Collins Police Department.

The witness described the perpetrator as a man who was wearing all dark clothes.

Investigators are asking for anyone with information regarding the suspect or the witness to contact Detective Dollie Knab at 970-416-2195. The witness is described as a woman in her mid to late 40s with brown, curly hair and was wearing multicolored glasses and a brown peacoat.

“This is a shocking crime that happened in broad daylight,” said Crimes Against Persons Sgt. Heather Moore. “We’re extremely grateful for the bystander who took action and intervened. We really need her to contact us and share anything she remembers so we can get this perpetrator off our streets.”