A color guard stood at attention and a lone trumpeter sounded a sorrowful rendition of the hymn "Amazing Grace" yesterday as more than 1,000 students and faculty of Coolidge High School in Northwest Washington mourned the death of 18-year-old classmate Andre Jackson, who was shot several times in the head outside his home Tuesday.

Coolidge basketball coach Frank Williams told the assembled students that Jackson, who last year spent more time on the bench than on the court, never groused about his reserve status and was always ready to jump into the lineup enthusiastically when called to do so.

"He didn't play a lot, but he was always very positive. He was always cheering the young men on the floor," Williams said.

Team captain Derrick Davis said Jackson was well-liked by the other players and never gave a hint that there was any trouble in his life.

"He was the type of guy who never told anybody his problems," Davis said. "He never talked about anything. He was the type of person we couldn't understand."

As several students broke into tears in the packed high school auditorium, where Jackson was praised as "a fine young man" and "one of the nicest kids around," indications emerged that there might indeed have been problems in Jackson's life.

Police, who were still trying to determine a motive in Jackson's slaying, said it may have stemmed from an apparently drug-related slaying last April. Jackson was seen as a potential witness in a trial stemming from the April 3 death of Alton Clea, 23, who was one of four men shot in a melee that ended in sudden gunfire.

Three other men were wounded in that incident. Five men, including one 16 years old and another 17, were arrested on charges of second-degree murder and are now awaiting trial in Superior Court.

Assistant U.S. Attorney Mark Hannon declined to comment yesterday on that case or on what role Jackson might have been expected to play in the prosecution. But friends of Jackson said it had become well-known in the neighborhood near his home that he was expected to testify.

According to police sources, Jackson at the time of his death was awaiting trial in the city's Juvenile Court on charges of possession with intent to distribute PCP, marijuana and cocaine. Jackson was arrested Aug. 10 in an apartment at 11 R St. NE -- one block from his home at 44 Q St. NE -- where vice officers executing a search warrant seized more than $11,000 worth of marijuana laced with PCP, more than $1,000 in cocaine, $6,217 in cash, a loaded .38-caliber pistol and numerous rounds of ammunition for a variety of weapons.

Jackson was one of five juveniles and four adults arrested in the raid at the apartment, which one police vice officer said had been under suspicion for weeks as a packaging and distribution point for illicit drugs sold on the streets of the surrounding community.

A woman describing herself as a friend of Jackson's family who last night answered the telephone at the home of Jackson's grandmother and guardian, Leona C. Barnes, said neither she nor any other family members wished to comment.

No arrests have been made in Jackson's slaying. Funeral services are scheduled for Monday.