Louisville police arrested a 17-year-old boy Thursday night on suspicion of sexually assaulting a 19-year-old woman last week in the 300 block of south McCaslin Boulevard.

The woman said she was walking outside around 9:30 p.m. on Sept. 21 when she noticed a man coming toward her, according to Louisville police. She crossed McCaslin and thought she was alone again until she noticed a shadow behind her.

She was grabbed suddenly around the neck from behind and dragged away from the street into some vegetation, where the alleged sexual assault occurred, according to police Chief Bruce Goodman. When the suspect grabbed the woman, he told her he had a knife, according to police, but it's unclear whether he used it.

After the alleged assault, the two walked north on McCaslin, and the victim managed to run to a Walgreens at 191 South McCaslin, where she called police. Louisville investigators interviewed people who they believed to have information about the crime, Goodman said, and that led officers to the 17-year-old suspect, who they're not naming because he's a minor.

Police, with the help of a Spanish-speaking Boulder officer, interviewed the teen with his father present Thursday evening. The boy acknowledged that he had sex with the victim in the location and at the time of the alleged assault, but he said it was consensual, according to police.

He was arrested on suspicion of sexual assault and assault in the second degree, and was booked into the Boulder County Juvenile Detention Center. The District Attorney's Office will file charges.