A 35-year-old man has been shot dead in a flat in the centre of Derry city.
Emergency services were alerted at around 11am and the scene was cordoned off.
Barry McCrory was shot in front of his partner, who was uninjured in the attack.
She was taken away in an ambulance in a distressed state.
Police and ambulance crews attended the first-floor apartment, above business premises in Shipquay Street, close to the Diamond.
Mr McCrory was known to police.
SDLP MLA for Foyle Pat Ramsey described the shooting as "an appalling and disgraceful incident".
He said: "I was in the vicinity this morning and heard the shots that have resulted in the tragic loss of life. There is a deep sense of shock in Derry city centre today."
Mr McCrory's death occurred less than 24 hours after the body of Kevin Kearney, 46, was found in a lake in north Belfast.
Police are so far treating the murders as two separate incidents.
Deputy First Minister Martin McGuinness said: "Over the past 24 hours two men have been murdered in Belfast and Derry. I condemn these murders without equivocation.
"Those responsible claim to be dissident republicans. They are not republicans of any shade. They are entirely motivated by criminal intent."
Tanáiste and Minister for Foreign Affairs Eamon Gilmore described the murders as vicious, brutal and cowardly.
He called on anyone with information to contact the PSNI.
Mr Gilmore said the people who claimed responsibility for the killings have no mandate and their actions lead nowhere.