Authorities captured 19-year-old Joseph Nelson of Raleigh in Charlotte over the weekend.
Investigators say two other suspects, 19-year-old Kwame Bellamy and 17-year-old Keith Mason - both of Raleigh, were arrested on Aug. 26. A third suspect, a 15-year-old, has also been charged with the robberies.
The first robbery happened at the Shop N Go on Highway 42 east around 8:45 a.m. An 18-year-old clerk was shot during that incident.
During a second robbery that happened around 10 p.m., a clerk at the Shop N Go on Highway 39 was shot. A coworker identified that victim as 62-year-old Wesley Davis.
Davis was shot twice -- once in the neck and once in the arm. He was taken to WakeMed, but his condition is not known.
The condition of the 18-year-old clerk also is not known.
Each suspect is charged with robbery with a dangerous weapon, conspiracy to commit robbery with a dangerous weapon, first-degree kidnapping, conspiracy to commit first-degree kidnapping, assault with a deadly weapon with intent to kill or inflict serious injury and conspiracy to assault with a deadly weapon with intent to kill or inflict serious injury.