CHICAGO (CBS) — A 31-year-old man has pleaded guilty to trying to rape a woman in a Foster Avenue Beach restroom in 2010 and has been sentenced to 20 years in prison.

Authorities said Joseph Mbatchou, of 941 W. Lawrence Ave., told police “She wouldn’t f— me, so I beat her ass,” after he was arrested on Sept. 28, 2010, for the attack at a beachhouse restroom at Foster Avenue Beach.

Mbatchou has pleaded guilty to attempted aggravated criminal sexual assault and was sentenced to 20 years, Cook County State’s Attorney’s office spokeswoman Lisa Gordon said.

The 37-year-old victim, who had been walking along the beach in the 5200 block of North Lake Shore Drive about noon that day, felt someone tap her on the shoulder when she was washing her hands in the restroom, prosecutors said. When she turned around, Mbatchou punched her repeatedly in the face, then slammed her head and face against a concrete wall when she tried to fight back by kicking him in the groin and scratching his face.

Mbatchou then dragged her into a bathroom stall and pushed her down on the toilet as he began to undo his pants and tried to pull off her shorts, prosecutors said.

A man walking outside heard her cries for help and ran into the bathroom, where he pulled Mbatchou off the victim, according to prosecutors.

Mbatchou allegedly punched the Good Samaritan before walking out of the bathroom and telling onlookers, “I’m FBI.” Some of those witnesses saw Mbatchou fighting with the man and called 911.

The victim, who identified the married Mbatchou in a lineup, had to have five stitches above her left eye. She also suffered contusions to her face, head and body, prosecutors said.

(The Sun-Times Media Wire contributed to this report.)