The incident happened just before 7 p.m. The man was standing in one of the library’s aisles when he “took his pants off in front of” the girl, according Arlington County Police.
The teen immediately ran to an employee and reported the incident, said ACPD spokesman Dustin Sternbeck. Police were called but by then the man had fled.
“The suspect is described as a black male in his forties, approximately 5’10” with a thin build,” said a crime report. “He was wearing a blue collared shirt and black sweatpants.”