David Berkowitz, a moody 24-year-old mail sorter believed to be the killer "Son of Sam," was arraigned in Brooklyn Criminal Court today on charges of second-degree murder.

He was held without bond and ordered to undergo immediate psychiatric examination after Brooklyn District Attorney Eugene Gold told Judge Richard A. Brown:

"Your honor does have before you today the 44-caliber killer, also known as 'Son of Sam.'"

Brown said Berkowitz "definitely may be an incapacitated person" and, therefore, may be unable to understand the charges.

Berkowitz, casually dressed in a light blue shirt and dungarees, looked slightly bemused. He did not speak during the brief proceeding. He was specifically charged with the July 31 killing of 20-year-old Stacy Moskowitz and the wounding of Robert Violante, 20, who was left virtually blind.

The second-degree murder charge was made because New York law permits first-degree murder prosecutions only in capital offenses, such as killing a police officer.

Two converging lines of clues - one a $25 parking ticket left on a car on a quiet street in Brooklyn, the other a neighbor's complaint about a bizarre hate campaign in a Yonkers apartment - led to his arrest as the man who has terrorized New York for more than a year.

Berkowitz, a former auxiliary policeman, surrendered meekly to detectives outside his apartment, reported on his way with a semiautomatic rifle to stalk his next victims in a discotheque either in the Bronx or the fashionable Hamptons in eastern Long Island.

Police said they found new notes, one of which warned that "Son of Sam" would strike again. Authorities said they also foud the .44-cal. Bulldog revolver the killer used in murdering six young people and wounding seven others.

Police Inspector Timothy Dowd, who headed the most intensive manhunt in the New York City Police Departement's history, said Berkowitz simply looked at him, smiled and said in a salutatory way, "Inspector."

As Berkowitz was being handcuffed and taken away in a motorcade of police cars late Wednesday night, Dowd said, Berkowitz said something to the effect that "this is the end of the line."

After questioning Berkowitz intensively for three hours early this morning, police said the suspect offered no coherent motive for the murders. Most of the victims were young women sitting in parked cars on secluded residential streets.

In a rambling and confused fashion, police sources said, he variously identified a 64-year-old neighbor named Sam Carr or Carr's black Labrador retriever - or both - as the spiritual, father-figure driving force that compelled him to kill.

Carr, in an interview with The New York Post, claimed that Berkowitz shot Carr's dog, Harvey, on April 27 with a 44-cal. revolver, and that the bullet is still lodged in the dog's hindquarters. Carr said Berkowitz wrote him seemingly demented letters threatening his life and that of his dog.

Authorities said that a similar hatemail campaign was launched by Berkowitz against another neighbor - a part-time Westchester County sheriff's deputy, and that some of those letters suggested it was the deputy who drove "Son of Sam" to kill.

The neighbor, Craig Glassman, 29, who lives one floor below Berkowtiz in an apartment house on the fringe of Yonkers' industrial section, received four letters allegedly from Berkowitz.

One of them, discovered after Glassman's apartment door was set afire last Saturday, read, "You will be punished, Craig," police said.

Then, almost incoherently, it continued, "How dare you force me into the night to do your bidding . . . True, I am the killer, but, Craig, the killings are your commands . . . The streets have been filled with blood, Glassman, at your request."

Asked why he became a target of the hate mail, Glassman conjectured, "I just happen to move in beneath him. He probably saw me in my uniform."

Glassman, who said he first thought the writer was "just a kook," had forwarded the earlier notes to Yonkers police, who routinely opened a file on the matter.

But after Glassman's door was touched Saturday and after he received the latest note on Tuesday, Yonkers authorities called the New York City Police Department's special "Sam" task force of 300 detectives and alerted them that Berkowitz might be a suspect in the killings.

Then began what Police Commissioner Michael J. Codd today called the "simultaneous development of parallel leads." That broke the case.

One lead was the Yonkers police detectives' suspicions of the Glassman antagonist, and the other was what Codd termed the "totally mundane, everyday, ordinary but vital clue."

That clue was provided by a middle-aged Brooklyn woman who was walking her dog the night the Moscowitz murder and noticed a cream-colored 1970 car being ticketed in front of a fire hydrant.

The woman, whom police refused to identify, told investigators she walked within five feet of the car's owner and noticed that he was carrying something in his outstretched right hand. As she raced home in fright, police said, she heard four gunshots in rapid succession, and for several days did not even notify police about what she had observed.

When she did, police began the tedious process of tracing all cars issued summonses that evening in the vicinity of the murder, and came up with the name of Berkowitz.

Deputy Police Chief Francis McLoughlin said today that when the Yonkers hate-mail tip came into "Sam" task force's Queens headquarters on Tuesday, one detective said, "Hey, that's one of the guys we had a ticket on."

Detectives Edward Zigo and John Longo said they went to the Yonkers police headquarters to check out Berkowitz, and then, almost as an after-thought, drove by Berkowitz' house spotted the cream-colored car.

In it they saw a canvas bag with the butt of a rifle poking out, one of "son of Sam" notes on the floor, and a bag of 100 to 200 shells. The discovery led to the stakeout that ultimately resulted in Berkowitz arrest as he was leaving the apartment.

Almost since the beginning of the investigation, Dowd and other commanders of the special unit had steadfastly maintained that "son of Sam" would be apprehended not in a dramatic and climactic Hollywood style confrontation, but by routine, dogged and uninspiring checking of the hundreds of tips that came in daily.

"It was an investigation in the classical sense of detective work," Codd said. "It was not the result of a sudden inspiration. It was the culmination of day-in work."

Nor were authorities surprised at the personality portrait of Berkowitz put together by friends, neighbors, co-workers and others who knew him, even if only in passing.

By all accounts, he is a brooding, explosive young man, given to outbursts of temper, days locking himself in his tiny efficiency apartment and constantly feuding with people he considers his enemies.

Detectives who talked with him said Berkowitz appeared to be tormented by a reality-fantasy conflict, just as some criminal psychiatrists had envisioned "Son of Sam" would be.

Codd confirmed that Berkowitz served from 1970 to 1973 as an auxiliary policeman in the Bronx, had worked as a uniformed guard for a security agency before joining the Postal Service and while in the Army was stationed in Korea.

Neighbors in the sprawling Co-op City apartment complex in the north Bronx, where Berkowitz grew up, said the suspect occasionally dressed up in uniforms, sometimes as a policeman or fireman or military officer.

Detectives and some forensic psychologists had speculated that "Son of Sam" might have been a former policeman - or a least a police buff - because of the military crouch he used while shooting his victims and the police jargon he occasionally used in his taunting notes.

Police said that while Berkowitz served with the 5,000-member uniformed New York City Auxiliary Police Patrol, he received training in police procedures but was not trained in firearms use. However, Codd noted, Berkowitz would have received weapons training after joining the Army in 1973.

The Army sifted through files at its records center in St. Louis, found 26 former soldiers named David Berkowitz, and narrowed them down to the man accused in the "Son of Sam" killings.

That part of the record made public showed that Berkowitz was reprimanded and "busted" once during his one-year tour of duty in Korea for missing a convoy movement. But he was later promoted back to specialist 4 from private first class.

Berkowitz's family life was unusual in that he was born David Falco and was adopted by Nathaniel Berkowitz at an early age, police said.

Police psychologists had speculated that the killer had childhoold psychological problems that resulted in him striking out at a mother image while trying to prove his worthiness to a father figure who had rejected him.

Jerry Moskowitz, whose daughter, Stacy, was "Son of Sam's" most recent victim, said after the arrest he wanted "five minutes alone with the guy."

"If they left me alone with him, I'd look at him and say 'Why?' Then I'd probably starts swinging. I don't swing easily . . . And I'd wipe the floor with the guy," Moskowitz said.

Pat Violante, who only hours before learning of the arrest had visited his partially blinded son, Robert, said, "What wonderful news. I'm so happy for other parents. This is wonderful.

"I don't want to think about bitterness. Any human, any father can feel bitter for his son if he thinks about it long enough."

Outside the Brooklyn Criminal Court, a crowd of more than 100 chanted in unison: "Kill! Kill! Kill the bastard!"