One of the most dramatic homicides in the District this year, a shooting on the grounds of Dunbar High School during school hours, has been brought to its courtroom conclusion with the first-degree murder conviction of Trey A. Manning.

Manning, 18, of the 4500 block of Seventh Street NE, was convicted of the premeditated killing of William Kemp with six shots from a 9mm automatic. The jury, which returned its verdict late Friday after a three-day trial, also found Manning guilty of carrying a pistol without a license.

Sentencing, set for Nov. 27, will leave D.C. Superior Court Judge Robert M. Scott little discretion. Under law, Manning must receive 20 years to life for the murder. The weapons violation carries a maximum additional sentence of one year.

Assistant U.S. Attorney Ronald Dixon told jurors that the Jan. 23 shooting arose from a grudge born two days earlier at Breeze's Metro Club in the 2300 block of Bladensburg Road NE. A friend of Manning's, according to testimony, made a sexual advance to the girlfriend of a friend of Kemp's on the dance floor.

"There was some pushing and shoving in the club, and this argument spilled out onto the street," Dixon told the jurors in his opening statement. "The seed was planted in Trey Manning's mind that night to take care of William Kemp."

About 3 p.m. outside Dunbar two days later, the prosecution said, Manning, who was not a student there, confronted Kemp.

"Then he tells people -- premeditation and deliberation -- 'Move back. Better move away,' " Dixon said. "William Kemp started to run away, but he couldn't run fast enough."

The government's evidence showed that Manning fired 10 shots, six of which struck Kemp.

Mark J. Rochon, Manning's lawyer, said Manning sided with a friend in the dispute at Breeze's but did not go to Dunbar two days later.

"This young man over here did not shoot William Kemp," he told the jury. "He was not the man who fired the bullets. He was not the man who had the gun . . . . He is not the man."