A Morehouse College student gunned down eight days before his 24th birthday may have been killed over drugs, Atlanta police said Thursday. While one man is in custody, a second suspect remains on the loose.

U.S. Marshals arrested Nicolas Ross Smith, 20, in Stockbridge and charged him with homicide and aggravated assault for the June 13 shootings that killed Joe Gibbs, according to Officer John Chafee.

“We are looking for a second suspect,” Chafee told The Atlanta Journal-Constitution. “At this time, the shooting appears to be related to a possible drug transaction between the suspect and victim.”

Gibbs, 23, was shot multiple times while behind the wheel of his car near the intersection of Parsons and Webster streets. He died before police arrived at the scene, not far from his college campus.

A passenger next to Gibbs was shot in the hand, but not seriously injured. Police have said Gibbs and his passenger were targeted.

Gibbs’ death came as shock to classmates and friends, including a former teacher and childhood classmate from his hometown of Culver City, Calif., outside of Los Angeles.

“Joseph has always been a kid that stays out of trouble,” Cherae Branner told the AJC earlier this week. “It’s just shocking, and it doesn’t add up.”

Branner said she and Gibbs grew up together and were more like family than friends. Gibbs planned to return to California to visit this summer, Branner said.

Instead, family and friends will gather for his funeral.

Gibbs, who would have turned 24 on Friday, lacked a few credit hours toward completing his English degree.

The funeral for Gibbs will be held Saturday at 10 a.m. at Angelus Funeral Home in Los Angeles. Internment will follow in Holy Cross cemetery in Culver City, Calif.