It was a year ago this week that members of the Best family gathered around a holiday dinner table and listened as the oldest of four sons made his surprise announcement: Robert K. Best had enrolled in the District of Columbia Police Academy.

The family was brought together again yesterday, this time by tragic news from a D.C. police official: Best, 24, had been shot to death early yesterday during a struggle with a suspected automobile thief, just one day after completing his rookie year.

"When he said that he wanted to be a cop I thought, 'It's a dirty job, but somebody's got to do it,' " Weston W. Little Sr., the slain officer's grandfather, recalled in an interview yesterday.

Lessie Little, the officer's grandmother who also helped rear him, began to shake as she recalled the maternal instincts that she felt that day last year.

" 'God, no,' " she said. "But it was his decision and I respected him for it."

D.C. police officers yesterday wore black tape over their badges as a sign of mourning. Police Chief Maurice T. Turner Jr. last night characterized Best's slaying as an "execution."

"I am deeply disturbed that an officer in the performance of his duty was shot down in cold blood without a chance," said Turner, visibly shaken. "These two men . . . have been involved in robberies, in parole violations, and they should have been in jail. Instead they are out on the street . . . . It's just a sorry thing that men like that have to roam our streets."

Described by family and colleagues as a dedicated officer well-versed in textbook police procedure and holder of a green belt in karate, Best and his partner, Officer William Haupt, were on a plainclothes patrol in an unmarked police cruiser at about 1:15 a.m. when they began chasing a red Fiat, which they believed was stolen, along Good Hope Road near Naylor Road in Southeast Washington.

According to a D.C. police spokesman, the two suspects in the Fiat fled for two miles, attempting to elude the pursing officers by heading into Prince George's County. But the Fiat skidded into a stop sign at Branch Avenue and Curtis Drive in Suitland. Both men jumped from the wrecked car and ran.

Haupt subdued the driver after a short chase, but the other suspect, Vincent Alexander Dark, 27, of the 2100 block of Douglas Road SE, fled behind the nearby Top of the Hill apartments with Best in pursuit.

Turner said that Best caught Dark behind a building, but did not suspect that Dark had a gun. When Dark, who police said was carrying a pistol in the waistband of his pants, pulled out the gun, Best raised his hands, Turner said.

"The suspect shot him Best in the hand, spinning the officer around, and then when he Best fell to the ground, shot him twice in the back," Turner said. One of the .38-caliber bullets ricocheted into the officer's heart, police said.

Best was pronounced dead at 2:55 a.m. at Greater Southeast Community Hospital.

Meanwhile, as other D.C. police arrived on the scene, officers Haupt and Edward Stulga began a manhunt for Dark, who spotted them and opened fire. The two officers subsequently caught Dark in a crossfire behind the building where Best had been shot. Dark, a high school dropout and ex-convict, was pronounced dead on the scene by the Prince George's County medical examiner. He had been shot six times, D.C. police said.

The second suspect was identified as Marvin Cornell Wilson, 30, also known as James Kerserson, of 1716 14th St. NW. He was taken into custody by Prince George's police and charged with theft, transportation of stolen property and possession of stolen property. He is also wanted in D.C. for a parole violation and a failure to appear on a court date.

Wilson was being held last night at the Prince George's County Jail, authorities there said.

Police said that the Fiat driven by the two suspects was stolen from Winston-Salem, N.C., on Dec. 8.

Best "was just the kind of person who would give 110 percent no matter what the job was," said his brother, Dave Best. "He just wanted to be the best."

Yesterday was the second time this year that a D.C. police officer had been shot and killed in the line of duty. On Sept. 14, officer Donald G. Luning, 31, an 11-year veteran, was fatally shot in the chest during a struggle with a man who he believed was driving a stolen car.

Washington Post staff writers Joseph E. Bouchard and Tom Vesey contributed to this article.