A District man was sentenced Wednesday to 40 years in prison for killing a Roosevelt High schoolmate in 2010, officials said.

Raymond Roseboro, 23, had been convicted in February of first-degree murder and related weapons charges in the shooting death of Prince Okorie, according to the District's U.S. Attorney's Office.

Prosecutors said that on the afternoon of Nov. 30, 2010, Prince and some friends were at home near the intersection of Seventh and Emerson streets NW in the Sherman Circle area when Roseboro appeared and asked Prince to walk with him to a store.

Two of Prince's friends joined him, and the group of four walked without any signs of tension. But shots rang out when the group was near the intersection of Delafield Place and Eighth Street, prosecutors said. One of Prince's friends testified that after Prince had fallen to the ground, he saw Roseboro standing near Prince, with a gun in his hand and a mean expression on his face.

An adult who was across the street from the shooting saw Prince lying on the ground and the shooter standing over him and firing at him. That witness described the shooter as having a hairstyle that matched Roseboro, according to prosecutors.

Roseboro was convicted in D.C. Superior Court on the third try after his first two trials ended in hung juries.

The defendant took the witness stand during his trials and said that on the day of the slaying, he walked home after school with his girlfriend and the couple then stayed there. He denied knowing Prince's friends and having ever hung out near the porch by Seventh and Emerson, officials said.

But prosecutors presented rebuttal witnesses during the most recent trial. One witness testified that Roseboro, Prince and the victim's friends had all hung out together on previous occasions near Seventh and Emerson streets. Roseboro's girlfriend at the time of Prince's slaying also testified, refuting the notion that they were at his home together at the time of the shooting.

During Wednesday's hearing, the government said that Roseboro may have killed Prince because he thought the victim was a potential witness in a murder case. Less than two weeks before his slaying, Prince was mentioned in a hearing as a possible witness against Eric Foreman, who has since been convicted of murdering Catholic University student Neil Godleski.

But Judge Russell Canan did not allow the suspected motive at trial because he thought there was insufficient evidence for it.