WASHINGTON — A 20-year-old Annandale, Virginia, man has been arrested for sexually assaulting a woman and roughing up a neighbor who came to her aid.

Fairfax County police say a 27-year-old woman was moving out of her apartment in the 7900 block of John Adams Court Tuesday afternoon when a man entered through an open doorway. Police say he implied that he had a knife and then sexually assaulted the woman.

A neighbor who heard the woman screaming rushed to help, and the suspect pulled the 37-year-old woman to the ground by her hair, police said, before running away.

Just 24 hours later, on Wednesday afternoon, detectives arrested Burhan Nurhussein Ahmed, 20, of Annandale. Police say he’s being charged with abduction with intent to defile, burglary with intent to defile and other sexual assault charges.