Twenty-year-old Steven Marcel Cooley, of Greenville, and 21-year-old Demario Quentel Williams, also of Greenville, were already in custody in Pitt County in connection with robbery charges there.
They were transported to the Wake County Jail on Sunday.
They joined 21-year-old Kwamane Everett and 20-year-old Dariel Haddock, both of Greenville, who were also in custody in Pitt County and were transported to the Wake County Jail on Saturday.
All four are accused of killing Majid Mohram, 39, during a robbery at M3 Tobacco on Calvary Drive last December.
Police responded to the scene of a shooting at that location near the U.S. Highway 1/401 split around 8:30 p.m. on Dec. 2, 2011.
EMS personnel determined Mohram had sustained a gunshot wound and transported him to WakeMed, where he later died.
Raleigh homicide detectives followed up on robbery arrests made in January by the Greenville Police Department and noted similarities between the M3 Tobacco Shop case and a Greenville robbery.