A muscular, curly-haired, out-of-work young white man, skilled in the repair of autos and fond of shooting, was indicted yesterday in connection with the wave of murders of black men in Buffalo last fall and winter.

The slayings, which kindled new fears and old racial tensions in industrial Buffalo, had been believed by a significant majority of blacks nationally to be part of the work of a racist conspiracy.

Although the suspect was indicted yesterday in connection with three of the murders, authorities indicated that their investigation has led them to believe that the seven murders in Buffalo, and perhaps five others elsewhere in New York state, were the work of one man acting alone.

Joseph G. Christopher, 25, a high school dropout who joined the Army last November after the first six killings in Buffalo, was charged in a sealed indictment with three counts of murder.

Authorities planned to begin processing papers today to have Christopher extradited from Fort Benning, Ga., where he was sent for basic training but ended up in the stockade on charges of stabbing a black soldier.

The murder indictment shocked friends and neighbors in the polyglot Italian, Polish and German working class community in east Buffalo where Christopher had lived.

According to reporters from The Buffalo Courier-Express who dug into his past, Christopher was remembered as a quiet, respectful young man, something of a loner but always anxious to perform errands or repairs for elderly neighbors.

His mother is a registered nurse, and his late father worked at a city incinerator plant. He had learned auto mechanics at a technical high school in Buffalo before dropping out eight years ago after completing the 11th grade. He was considered by acquaintances to be a very good mechanic, although none could remember his ever holding a steady job.

He was not remembered as having strong racial or political views. In his predominantly white neighborhood, however, resistance to black migration from the center of the city has been strong.

Christopher owned guns, had a pistol permit and had belonged to shooting clubs since he was a teenager. Police seized guns and shell casings at his home and at a vacation property in a rural area south of Buffalo as part of their investigation.

In a bloody 36-hour period last September in Buffalo, the same semi-automatic .22-cal. weapon was used to kill a black teen-aged boy and three black men.

On successive days, two weeks later, the battered bodies of two other victims, both black and both cab drivers, were found on remote roads in the Buffalo suburbs. Their chests had been cut open and their hearts carved out.

The seventh slaying, the victim a black man waiting at a bus stop in Buffalo, occurred Dec. 29, a time when Christopher, who was assigned to Fort Benning on Nov. 19, was home on Christmas furlough. Another black man was stabbed to death at a bus stop in Rochester, 70 miles east of Buffalo, on Dec. 30.

In New York City, four dark-skinned men were stabbed to death and two others were wounded by a knife-wielding attacker on Dec. 22.

Two New York City investigators traveled to Fort Benning to see Christopher over the weekend, and others consulted with Erie County (Buffalo) District Attorney Edward Cosgrove yesterday.

The break in the case came not from massive detective work but from comments Christopher made earlier this month while a patient in the base hospital at Fort Benning. m

He was there being treated for what a base spokesman described as a self-inflicted cut while in the stockade when two nurses allegedly overheard him telling someone about the slayings in three New York cities. The nurses were flown to Buffalo, where they provided testimony to a grand jury shortly before the indictment was issued.