A West Baltimore handyman known for fixing appliances and mowing lawns for free was charged last night with fatally shooting a 15- year-old boy in the back yesterday, apparently enraged that the teen-ager was trying to steal a bicycle from his yard, police said.

Edward Day, 54, known to neighbors as a Vietnam veteran with the nickname "Mr. Fix-it," was taken into custody about 9 p.m. while riding a bicycle a block from the scene of the shooting.

Investigators said Day was charged with first-degree murder and a handgun violation. He was being held last night at the Cental Booking and Intake Center pending a hearing today.

The killing - in a well-kept neighborhood that Day often clipped and groomed himself - appears to be the latest example of vigilante justice by city residents taking aim at troublesome teens. Such cases often create a storm of debate because they are seen by many as exemplifying the frustrations of living in Baltimore's crime-ridden neighborhoods.

Relatives and friends of the slain youth, David Stewart, said last night that Day should be prosecuted for killing a boy who had done nothing more than attempt a petty crime - that of stealing a 10-speed bicycle.

"He killed my son, and my son did no bodily harm to him," said Marnice Cooper, Stewart's mother. "He needs to be arrested. My son was just a child."

About 3 p.m., Stewart was riding his dirt bike with a friend in the alley behind Day's rowhouse in the 2300 block of Harlem Ave., noticed a red 10-speed in Day's back yard, walked through a gate in the fence and tried to steal it, police said.

Day came out of the house and fired once with a double-barreled shotgun, hitting Stewart in the back from 10 feet away, police said.

Stewart, of the 2700 block of W. Lafayette Ave., died a short time later at the Maryland Shock Trauma Center, where his mother and father identified the body.

He is Baltimore's 142nd homicide of the year.

After the shooting, Day put the 12-gauge shotgun in his bedroom, then rode one of his bicycles to a pool hall, police said. Officers said they found a spent shotgun shell in his pocket.

Day told investigators that he hadn't shot the youth, but slipped on the grass as he walked outside his house and the shotgun discharged accidentally. He told detectives he had been having problems recently with children entering his yard and stealing, police said.

After the shooting, police and crime lab technicians combed the yard for clues. Stewart's blue Huffy was still resting against Day's fence and the 10-speed was leaning against his wall, under a green aluminum awning. Two lawnmowers sat in the grass.

Residents in Day's neighborhood - many have lived there for decades - described the handyman as an eccentric known for fixing televisions and children's bicycles for free.

They said Day has lived in the block for most of his life, but did not apparently have a full-time job. Residents said he might have collected veteran's benefits and cut lawns, trimmed hedges, and fixed appliances and bicycles for cash. They called him "Mr. Eddie" or "Mr. Fix-it."

Some in the neighborhood said the killing reminded them of one of the city's most notorious vigilante shootings - that involving Nathaniel Hurt, a 61-year-old retired steelworker who in 1994 fatally shot a 13-year-old vandalizing his car. Hurt went to prison for 14 months for killing Vernon Lee Holmes Jr., after an emotionally charged debate about how far citizens can go to stop nuisance crime in their neighborhood.

Like Hurt, a man known for sweeping neighborhood alleys and sidewalks and operating a snowball stand for children, Day also is known for taking care of the block he lives in.

A woman said Day had just repaired her television, which was having trouble with reception. Another said he swept the sidewalk in front of her house.

Day could often be found in his back yard working on bicycles, which he often rode around the neighborhood.

"They were his transportation, his car," said Jason Albright, 23, a neighbor.

Children and adults alike said they like Day because he fixes their bicycles and loans them his own.

"He let us ride his bike to the store," said Albright. "There was no need to go stealing it. ... He was cool."

Vernon Jones, 74, said he paid Day $65 one recent afternoon to chop down two trees and remove the debris from his yard.

"He was very kind-hearted," Jones said. "He wouldn't charge you much."

But Jones and other neighbors also described Day as "a little off." He wore heavy coats in hot weather, Jones said, and often muttered to himself.

Day's relatives said he is a good man who would never harm anyone, much less a teen-age boy. They said they didn't know he owned a shotgun.

Records show that Day was charged twice in 1989 with firearms-related charges. Both cases were dropped; details were not immediately available.

Ronald Lynch, 26, a nephew who uses a wheelchair, said Day would help carry him up stairs without hesitation and gave him money whenever he needed it.

"He helped kids, everybody," Lynch said.

Residents credited Day with helping keep his block neat - trimming nearly every hedge, cutting most residents' grass, and sweeping the sidewalk and street.

"This is a hidden treasure," said Armenta Jones, 58. "Go two blocks and you're in Hell's Kitchen. He really did a lot more."

A few blocks away, David Stewart lived with his mother. Relatives said he loved riding bicycles and raising dogs, especially his year-old pit bull Bronco.

He spent hours looking through books, seeking better ways to train and feed the dog.

He was attending summer school after finishing his freshman year at Walbrook High School. He wanted to be a professional basketball player.

Stewart, who had two younger sisters, was known as a jokester, often popping off a wisecrack at someone's expense, but always in a light-hearted way.

"He was just the life of the block," said his friend Sherrice Cary, 19. "It will never be the same again. It's a shame what happened, a real disgrace."

In a photograph taken just after Christmas, Stewart stands next to his 12-year-old sister Dearia. He is cracking a smile while pursing his lips. Half of his hair is a fluffy dome, the rest is combed tightly to his scalp.

"He was just a happy child," his mother said. "He was like my little brother. He made everybody laugh."

Yesterday's shooting is one of a handful in the past decade that have involved a Baltimore youth killed while stealing or vandalizing property.

In July 1998, Albert Sims, 78, shot a 15-year-old boy, Jermaine Jordan, after his Cadillac was hit with a brick in the 1600 block of Llewelyn Ave.

Sims, the only resident of a block filled with vacant and boarded-up houses, was eventually found not competent to stand trial and committed to the Clifton T. Perkins Hospital Center, the state's facility for the criminally insane.

Some residents who lived a few blocks away sided with Sims, saying that local teens had broken into his house several times and were frightening him.