A 17-year-old girl was assaulted Wednesday at the Thomas Jefferson Library in Falls Church.
The girl noticed a man watching her as she studied. When she felt intimidated as she was leaving, she ducked into a restroom.
"Within seconds, he followed her," said Lucy Caldwell of the Fairfax County Police Department. "She yelled at him to get out... and then he touched her and assaulted her."
The girl kicked him and screamed for help, and he fled the scene.
Police described the suspect as a black male from 5'7" to 5'10," with a shaved head, a diagonal scar on his forehead and a gap in his front teeth.
Library workers told police they had seen him before, but weren't aware of any previous incidents or violent behavior.
"Very scary, and I'm very, very concerned about it," said library patron Rajan Bhandary, who is the father of a 14-year-old girl. He said he planned to talk to her about the incident.
The victim is shaken up, but wasn't physically harmed, police said.
CORRECTION: An earlier version of this story said the teen was sexually assaulted. A Fairfax County Police spokesperson said that unwanted touching is considered an assault, but it was not sexual in nature.