They were driving around in an unmarked police cruiser, hunting a serial slasher targeting random women. It was the night after the latest attack had become public, as fear began to settle into Northwest Washington’s Petworth neighborhood.

About 11 p.m. Thursday, Sgt. Christopher Baxa and Detective Matthew Dailey spotted a man who fit the attacker’s general description standing at the top of Sherman Circle. Baxa walked up, noted the man had a dazed look and saw what appeared to be dried blood on the right leg of his khaki pants.

Police said in court documents that the man told them that he had been in a fight, and he had a small folding pocket knife with a silver blade and a brown handle.

That stop didn’t lead to an immediate arrest, but police used the information to get a search warrant the next day. Inside a home the man shares with his mother, police said, they found three sets of clothing similar to those described by three of the four victims, including the khaki pants.

Garey Jones III, 20, who lives two blocks from where police had questioned him, was arrested after the search and charged Saturday with assault with a deadly weapon in connection with a June 19 attack on Allison Street. Police said they also believe he is responsible for three other stabbings, on May 5, June 10 and June 14.

“It was just great detective work,” said Police Chief Cathy L. Lanier, who after the arrest told residents, “I think the danger has passed.” None of the victims were seriously injured.

No one answered the door at the two-story rowhouse on Emerson Street where Jones lives; neighbors said the family has been gone since the police raid Friday night. Jones’s attorney did not return calls seeking comment; the suspect is due in D.C. Superior Court on Tuesday for a preliminary hearing.

Authorities have not established a motive for the stabbings — three in Petworth, one farther south in Bloomingdale — but the suspect’s mother told police that her son had been punched in April so hard that his jaw broke and that it had to be wired shut for a time, court papers say. He was then given a diagnosis of schizophrenia and bipolar disorder, she told police.

Two neighbors who have known the family for the 10 years it has lived on Emerson Street expressed surprise at Jones’s arrest. They described Jones as lanky, shy and quiet and taciturn. Neighbors said he attended college last year, but they did not know where.

Lawrence Allen, who lives across an alley from Jones, said he took 10 to 15 minutes a day to chat with the young man.

“He just wanted someone to give him some direction,” Allen said. ”He was really a good guy.”

Allen, who is 52, is having work done on his house, and the contractor he hired threw Jones some jobs. But what Jones really wanted to do, Allen said, was cut a CD with his rap music, “and sell them on the street for five bucks each.”

“I just hope and pray it works out for him,” Allen said of Jones. “I just don’t understand this. He is a young man who everyone on the block liked. He didn’t cause trouble. He didn’t hang out with gangs. He just seemed a quiet, average guy.”

It’s unclear if the pocket knife police said Jones had was used in the attacks; victims were unable to describe the weapon. The woman attacked on Allison Street told police that she was stabbed with a silver tipped object concealed in the man’s right hand, squeezed between his thumb and index finger.

That woman said her attacker wore khaki pants and a faded navy blue nylon v-neck pullover with gold trim on the neck and gold stripes on the cuffs. Among the items found in Jones’s house, police said, were khakis and a Notre Dame v-neck navy blue pullover jersey with gold trim around the neck and gold stripes around the cuffs.

But police said in court documents that the same victim failed to identify Jones from a photo array, instead choosing a picture of another man who looked similar.

Lanier told reporters that the woman was attacked from behind at night and that she remains confident that the case will stand given the other evidence found in the house.