The RUC is questioning a man about the murder of Protestant taxi driver Mr Trevor Kell in north Belfast last week.
It is understood a second man is wanted for questioning about the shooting. Mr Kell's murder was followed by three loyalist gun attacks in which a Catholic man was killed and two men were wounded.
The RUC Chief Constable, Sir Ronnie Flanagan, has blamed republicans for killing Mr Kell. However, the Provisional IRA, the Continuity IRA and the "Real IRA" in Belfast have denied involvement.
Meanwhile, a man was charged in Belfast yesterday in connection with the attempted murder of Mr Paul Scullion, a 24-year-old Catholic, shot in the Oldpark area last week.
Mr Mark Needham (18), a sales assistant, was accused of withholding information about the loyalist murder attempt. He was remanded in custody.