Two men remain in police custody in the North this morning in connection with the murder of Emmett Shiels in Derry.
The 22-year-old was shot dead in the Creggan estate in the early hours of Tuesday morning after apparently intervening in a row between a group of masked men and local youths.
Dissident republicans are being blamed.
The two men in custody, who are in their late teens and early 20s, presented themselves for questioning at a PSNI station in Derry on Tuesday night.
The police are also examining a car which they believe may be linked to the murder.