Teddy Garvin, a 17-year-old Ballou High School senior shot to death as he sat on a Metro bus Friday evening, was the victim of an unprovoked, random act of violence, police said yesterday.

Appealing to the public for help in identifying suspects in the shooting, police yesterday sketched this account of what they believe happened:

Garvin was on his way to his girlfriend's house on an evening so fresh the windows were open on the A2 bus he often rode. The bus had paused to pick up passengers when a hand holding a gun suddenly reached in the window. There was a loud bang.

It was not clear to occupants of the bus what had happened, police said. Hearing the noise, the driver asked whether everyone was all right. After being reassured that the roughly 40 passengers were fine, the driver pulled away in the 4200 block of Wheeler Road SE and drove another nine or 10 minutes before someone reported that the young man sitting nearby had slumped over.

Garvin was pronounced dead a short time later at D.C. General Hospital.

"Yes, it was a random shooting," Lt. Willie Dandridge, of the D.C. police department, said at a news conference yesterday. Dandridge declined to say what evidence supported that view but emphasized that police believe Garvin was not a specific target.

The violence shocked operators of the Metro system, who could not recall a similar incident.

"We provide one of the safest transportation environments in the world," said Polly Hanson, deputy chief of the Metro Transit Police. "We don't have people running up to bus windows shooting in."

Garvin--an athlete who, according to his family, planned to enter Howard University next year on a tennis scholarship--was struck by a bullet in the right armpit as he sat next to the window near the rear of the bus on the right side.

Dandridge offered no motive for the shooting in the Barnaby Terrace neighborhood. When a reporter at the news conference asked whether a member of a gang active in that section of the city could have fired the gun, Dandridge called it a "possibility" but said police are considering almost any scenario.

"Right now, everything is a possibility," he said.

Talk of gangs does not apply to Garvin, Dandridge emphasized. "To our knowledge, he was not involved in any kind of criminal activity," he said.

Just before boarding the bus about 7:15 p.m., Garvin called his girlfriend, Shauna Lowery, 20, from a pay phone at Greater Southeast Community Hospital near the bus stop. He told her he was on his way, and he asked whether their son, Teddy Jr., was ready for a planned visit to Garvin's father's home in Northeast.

The young man didn't know it, but Lowery planned to surprise him by showing that "T.J.," 8 months old, could take his first few steps on his own.

"Boo, I hear the bus," Garvin told Lowery. "I love you."

Family and friends gathered to mourn and remember yesterday in the yellow house with brown shutters on Ninth Street SE where Levelle Garvin, the young man's grandmother, raised him and his three brothers.

"It's still unbelievable," said Angela Garvin, one of Garvin's aunts. "He was the last person you would think something like this would happen to."

The family's anguish was deepened when investigators initially misidentified the victim as Samuel Garvin--Teddy's younger brother. Believing the police, the family thought Samuel was dead Friday night--until he called home. When Teddy was unaccounted for, the family stayed up much of the night praying for him, unable to get answers from the hospital, police or the morgue. Police continued to identify the victim as Samuel in public statements until yesterday afternoon.

Teddy Garvin was described by those who knew him as talented and energetic. Darrell Watson, director of the Ballou marching band, in which Garvin played trumpet, said: "Teddy was an exceptional young man. . . . He was well known around the school, friendly and outgoing. He was a true motivator, a good friend and an excellent student."

Garvin played in the local Arthur Ashe tennis program, and when he wasn't playing, he liked to teach the sport to his young cousins or watch it on television.

Lowery said Garvin played an active role in raising their son. He said he used to joke that once T.J. could walk, he would teach the boy how to play tennis.

"He never got to see him walk," Lowery said.

CAPTION: Ballou High School senior Teddy Garvin, 17, shown in a two-year-old photograph, was shot Friday night on a Metro bus in Southeast Washington.