The brother of the suspect in the April 2000 slaying of 8-year-old Kevin Shifflett was shot and killed yesterday outside his home in Alexandria, police said.

Police said David C. Murphy, 37, was working on his 1989 Ford pickup truck on one of Alexandria's busiest streets at the height of the evening rush hour when someone approached him, fired several shots and fled.

Murphy, whose truck was parked in front of his house in the 400 block of North Patrick Street, was pronounced dead at Inova Alexandria Hospital about an hour after the 5 p.m. shooting.

Murphy was the older brother of Gregory D. Murphy, 34, who has been declared mentally incompetent to stand trial in Kevin's slaying. Last week, a judge ordered him to continue receiving treatment that one day might enable him to face the charge in court.

Gregory Murphy was arrested five years ago and charged with stabbing Kevin as he played on the sidewalk with other children outside the Del Ray home of his great-grandparents.

In the frigid late-afternoon darkness yesterday, police officers canvassed the area in search of witnesses to the slaying, the third in Alexandria this year. Police said they knew of no motive and had no idea of the shooter's identity. Witnesses told police that the shooter had run north on North Patrick Street.

"There was a tragedy that occurred in the city tonight, and now we have to get to the bottom of it," said Capt. John Crawford, a police spokesman. He said it appeared that David Murphy was targeted.

"You have a guy who was outside working on his truck, and we don't know who shot him or why. . . . It was for no apparent reason that we can figure out right now," Crawford said.

Police cordoned off the block with yellow tape, though neighbors milled about. Several large lights were aimed at Murphy's weather-beaten truck, which was parked at the curb, its hood still upright as detectives collected evidence.

Bobby Mahoney, a lifelong resident of Alexandria, stood last night near the scene, a residential block at the edge of Old Town with tidy rowhouses and tree-lined sidewalks. He said he heard the sirens, looked outside and saw a fleet of emergency vehicles rushing past. He followed the lights, he said.

"It's relatively safe around here, and so this is scary, especially knowing that the person who did it is still on the loose," said Mahoney, 28. "This is a busy area, and so it's really troubling."

Crawford said a police substation is located around the corner from where the slaying occurred. Officers heard the shots and flooded the area just moments afterward. Traffic was diverted around North Patrick Street (Route 1).

He asked that anyone with information about the slaying call the department's criminal investigations section at 703-838-4711.