CHICAGO (CBS) — A 34-year-old man is charged with a felony – accused of impersonating a Chicago Police officer and attempting to rob and sexually assault a man in Wrigleyville on Sunday morning.

Police said it was about 5 a.m. when 34-year-old Daniel Grunauer of Chicago stopped a 21-year-old man on the street near Fremont and Byron. Grunauer told the man he was a police officer and that he was under arrest.

Daniel Grunauer (Credit: Chicago Police)

Authorities said Grunauer tried to rob and sexually assault the man.

An off-duty police officer stopped the assault, according to a police report and now Grunauer is charged with impersonating an officer, a felony and a misdemeanor count of battery.