A 39-year-old Alexandria man was found slain in his home early yesterday, and police said they believe the Marine Corps computer specialist was stabbed to death.

A concerned neighbor went to check on Ray Heidebrecht about 3:30 a.m. and found his body, with an apparent stab wound, in Heidebrecht's black-and-white duplex in the 300 block of LaVerne Avenue, police said.

An autopsy will be performed today to determine how and when Heidebrecht died, police said. They said that Heidebrecht lived alone and that they are searching for his maroon 1999 Isuzu Rodeo, with Virginia license plates YTG 7844.

Police said they have no motive or suspect in the slaying, the second in the city this year.

"We haven't established a motive, and we do not know the relationship, if any, of the victim and the suspect," said Amy Bertsch, a police spokeswoman. "We are looking for anyone who may have seen the victim over the weekend, especially from Saturday evening to Sunday night."

Heidebrecht lived on a quiet tree-lined street in a middle-class neighborhood known as Mount Jefferson, which is wedged between Mount Vernon Avenue and Jefferson Davis Highway.

Lt. Ray Hazel, the police liaison to the community for the last 15 years, said residents of the neighborhood look out after one another and can often be seen out walking in the morning, picking up trash. Crime problems in the community are few and have been mainly "nuisance-type crimes," including petty property crime, some drug dealing and people hanging out on street corners, he said.

"The city doesn't have a lot of homicides," Hazel said of Alexandria, which averages seven homicides each year. "When they occur, they get a lot of attention."

Duane Shields, president of the Mount Jefferson Civic Association, said Heidebrecht was a good neighbor who "kept the house in great shape." He said residents have been working hard to improve the neighborhood, a mix of all ages and races.

"We're completely caught off guard on this," Shields said.

Heidebrecht was the information systems management officer at the headquarters battalion at Henderson Hall in Arlington, said Capt. Mike Newman, a spokesman. He had worked as a civilian for the Marine Corps since December 1989, he said.

"He was one of the most conscientious, hard-working people we've had in the battalion," said Lt. Col. Wayne Briggs, deputy post commander at Henderson Hall, who worked with Heidebrecht. "A lot of people here are devastated. Ray would bend over backward to help somebody out."

Police circulated fliers in the neighborhood yesterday with a photograph of Heidebrecht's smiling face. They offered a reward of up to $1,000 for information leading to the arrest of the person or people responsible. Anyone with information was asked to call Detective Bill Scott at 703-838-5033.

CAPTION: Police said they had no suspect in the slaying of Ray Heidebrecht.