The second of two 20-year-old suspects is now jailed in the shooting death of a Morehouse College student. And additional arrests are possible, Atlanta police said Monday night.

“This case is not closed yet,” Officer John Chafee told The Atlanta Journal-Constitution.

Investigators are asking for the public's help to identify two men in surveillance video from a gas station about an hour before the June 13 shootings, Chafee said. But police declined to say what role they believe the two in the video had in the death of Joe Gibbs.

The video was released three days after police announced the arrest of a second suspect in the homicide.

U.S. Marshals arrested Devin Richard Campbell on homicide and aggravated assault charges, Sgt. Greg Lyon said. Campbell was booked into the Fulton County jail Friday and was being held Monday without bond, booking records show.

Campbell is the second man accused of killing Gibbs, who was shot multiple times while seated behind the wheel of his car, according to police. Gibbs, 23, died before police arrived near the intersection of Parsons and Webster streets, not far from his college campus. A passenger in the car survived after being shot in the hand, police said.

Nicolas Ross Smith was arrested Thursday and also charged with homicide and aggravated assault, police previously said. Police have said the shootings may have been drug-related.

Gibbs, a California native, would have turned 24 on Friday. His funeral was held Saturday in Los Angeles.

An English major just a few hours short of his degree, Gibbs participated in the May graduation ceremony, where President Barack Obama spoke.

Anyone with information on this homicide is asked to contact Crime Stoppers at 404-577-8477.