D.C. police believe they know the identity of the fourth suspect in a South Capitol Street massacre, the Washington Examiner has learned.

The 21-year-old is already wanted on a bench warrant after he missed a hearing for an unrelated marijuana and alcohol case, a police source said and court records confirmed. Detectives have quietly asked street officers to pick him up on the marijuana warrant and to hand him over to the homicide unit for questioning, a source with knowledge of the investigation said.