A woman was sexually assaulted and robbed in her Chantilly area residence by a teenage boy who ambushed her as she arrived home Monday morning, police said.

The attack occurred around 9:30 a.m. in the 13200 block of Leafcrest Lane, Fairfax County police said. As the woman unlocked a door, police said the teen came up behind her and forced her inside.

The suspect displayed a knife and then assaulted the 29-year-old, police said. He fled on foot after the woman screamed, police said. The victim was not injured and it appears she did not know her assailant, police said.

The suspect is described as black male, 15 to 16-years-old and about 5’7” tall. He is thin and was wearing a shirt and blue jeans at the time of the incident, police said.

Officer Bud Walker, a Fairfax County police spokesman, said authorities were concerned that the attack happened in broad daylight and said woman should be on guard in the area.

Anyone with information is asked to call Fairfax County police at (703) 691-2131.