Arlington County Police have launched an intensive manhunt in the Halls Hill area for a person they believe responsible for four rapes during the past year.

The Halls Hill area of North Arlington is bounded by Lee Highway, Washington Boulevard, Glebe Road and George Mason Drive.

Police are calling the acts "brutal sexual assaults" and label the assailant, who uses a butcher knife during the attacks, "an extremely dangerous criminal" who is becoming increasingly violent with each successive attack.

"I stay awake nights worrying that I'll get a call saying he has now committed a homicide," says Dectective Kenneth Adams, who has been working on the unsolved rapes for the past year.

The most recent attack took place on Dec. 1 when a single woman, aged 42, got off a Metro bus along Glebe Road in the early evening. The woman was dragged at knifepoint behind two construction trailers where the assailant attached her, slashed her across the face with a butcher knife and stole her purse.

The four victims, one black and three white, live in the same geographical area. Ages of the women range from 28 to 43. Three of the women are married, one is single. All were attacked in the early evening.

Police say the assailant always steals a butcher knife from a neighborhood drug store or supermarket and drops the wrapper at the scene of the crime. A purse snatcher in the same area two years ago also dropped a knife wrapper after attacks, which leads police to believe the rapist is the same man.

"You could say he's now progressed to rapes," says Adams.

Arlington Police records show 41 rapes in 1980, but say the four attacks in the Halls Hills area are the only ones that appear to be perpetrated by the same person.

Friends of the most recent victim have raised a $1,000 reward for information leading to the arrest and indictment of the woman's assailant. Police say all information will be treated confidentially.

Until the rapist is apprehended, Arlington police are warning women in that area to refrain from walking outside alone after dark, and to be especially careful when getting off Metro buses in the evening.

"I hate to see and say those things," Adams says, "but doggone it, we don't want him to strike again before we catch him."

Police patrols have been beefed up in the area and composite drawings are being distributed of the suspect, who is described as a black male, in his mid-20's, with a muscular build and no facial hair.