He has been in prison since the spring, much of the time confined to a cell all but three hours a day, "protected" from retribution by the other prisoners because of his offense. His is the crime which, for many Bostonians, has become symbolic of the racial violence that has plagued this city since its schools were desegrated in 1974.

A bullet he fired from a handgun while crouched on the roof of a public housing project in the poor white neighborhood of Charlestown penetrated the neck of a high school football player from the poor black neighborhood of Roxbury -- leaving 15-year-old Darryl Williams a quadriplegic.

The September 1979 shooting to which Stephen McGonagle pleaded guilty seemed to convince much of this city of the depth of its racial problems -- to confirm the whispered limits on blacks who consider traveling in white neighborhoods. It sparked six weeks of racial turmoil in Boston's schools and prompted its clergy to undertake a continuing campaign for racial tolerance. The city has renamed its all-star high school game to honor the victim of what is widely assumed to have been a random, racial sniping.

But the story of Stephen McGonagle tells about himself is far more complicated than a clear-cut case of racism. It is a story about gangs, guns, and a kind of white poverty unknown in most cities.

At 18, the face behind the trigger in what is referred to here as the "Darryl Williams incident" is still boyish, out of place in the Norfolk state prison where McGonagle could spend 20 years. He is muscular and athletic and wears the dungarees, t-shirts and sneakers common to white Boston street kids. He prefers the "I'm proud to be a Townie" shirts with shamrocks popular in his native Charlestown, an island of rowhouses and housing projects in the shadow of the Bunker Hill monument.

He, in fact, insists he was not motivated by race, but is open about the fact that race is often on the minds of his fellow "Townies."

"When you grow up in Charlestown, you learn when you're young that Charlestown is racial," he says matter-of-factly. "It's known for being racial. You have kids 3 or 4 years old runnin' around [talking about] 'niggers' and they've never even seen one."

Blacks are viewed as an economic threat.Affirmative action programs are not popular in a white neighborhood where, according to city figures, 24 percent of all families live in poverty.

"People say that when blacks bitch they get what they want," says McGonagle, "but there's nothing for white people."

"You hear people say how we can't let a black family into the town or the whole town will go black. Roxbury used to be white, they say."

Blacks, says McGonagle, are thought to bring with them "low crime.

"Charlestown has its problems. It's not really that nice a place to live. But there's no low crime like in Roxbury. People rob banks and there are fights and stabbings, but there's no purse snatchings or muggings."

Racial feelings are not always overt, but they can easily boil over on the street corners of Charlestown and other blue collar neighborhoods, where kids like Stephen McGonagle can be found on all but the coldest nights.

Police blame much of Boston's racial violence on youth gangs -- and there are hundreds of them, almost all white. They are informal groups which gather on corners and in playgrounds throughout the city. Gangs are ranked as Boston's top public safety issue, according to city surveys of residents. "The racial problem here can't be viewed apart from the overall youth problem," says Michael Donovan, former assistant to Boston Police Commissioner Joseph Jordan.

His view is echoed by Walter Miller of Harvard's Center for Criminal Justice, who is currently completing a Justice Department-financed survey of youth gang problems nationally. "Time and again," says Miller, "incidents advertised as strictly racial in Boston tend to be gang related."

Stephen McGonagle's career in a gang began a few months before the incident that changed his life, about the time he left high school. He had attended only sporadically, he says, generally choosing to "hook" rather than be bused to Roxbury.

After "joining" the gang, his days on the corner would often begin late, he recalls.

"There was no schedule. I might sleep all day if I wanted to." Often, he says, he would get up in the early afternoon, then walk across the width of the town, bound for The Godfather, a pizza parlor in the Charles Newton housing project.

"If you don't hang in a gang, a lot of people will think you're a sissy," he says. "You gotta do something. I love sports but there's not even a bowling alley in Charlestown."

Gang membership comes too, says McGonagle, from frustration. He recalls filling out job applications at the candy and sugar factories which are Charlestown's largest employers -- and never hearing from them.

"People look down on you if you say you're from Charlestown. They think you're a bank robber." It's that lack of prospects which motivates gang membership, says McGonagle. "A lot of kids just have nothing to look forward to. They're bored."

"Life on the corner provides entertainment. What you do depends on your mood," says McGonagle. "You might play football or hockey in the street. You might wrestle. You might just listen to disco and drink beer."

"The Irish love to drink," says the 18-year-old, "especially the low Irish." Gang members wear running shoes, he says, to make it easier to make off with the beer when police arrive, as they do during periodic gang crackdowns.

And along with beer, there were guns. "Guns are as common as cars in Charlestown," says McGonagle. "People go around shooting them off like toys. Some do it for fun, some do it to be macho." Some do it in fights as well. Five kids with whom McGonagle grew up, he says, have met violent deaths.

But firing a gun for pastime is what Stephen McGonagle insists he was doing on the roof of the Charles Newton project last fall. In his version of events that day -- never made public in the trial because of a plea bargaining arrangement -- his routine the day he shot Darryl Williams was little different than his normal day on the street. To him, the Williams shooting was just another deal from the bottom of the deck. He fired at a bottle on a rooftop, he says, but missed. It was a stray bullet that happened to hit the black player in an integrated huddle. It is a version of events that police and even some close to the victim's family find somewhat credible. The 300 yards from the project's roof to the football field next to Charlestown High School is a long distance to fire a pistol accurately.

But ironically, McGonagle freely admits knowing and associating with those who are likely to commit just the kind of random racial attack of which he is widely thought to be guilty.

Almost any stranger passing The Godfather could face trouble, he says.

"It depends on how you act," he says. "If you just walk straight ahead and mind your own business, you might not be hassled. But if you stare, you're in trouble."

What would happen if the stranger passing by happened to be black? McGonagle shakes his head silently for a moment.

"It depends on what mood people are in. It might be a brick. It might be a bottle. It might be a knife."

Stephen McGonagle today expresses remorse over the shooting for which he will be in prison at least until April 1982.

"I think about him [Williams] a lot," he says. "I've thought about maybe getting a priest to write a letter for me. I've thought about charging for interviews and sending him the money."

McGonagle said he hopes not to return to the corner when he leaves prison. He would like to become a tradesman, perhaps a carpenter or an electrician. But his ties to the street life are nevertheless strong.

Many nights in prison he goes to the pay phone to call "home" -- another pay phone near The Godfather pizza parlor.