The family of Mr Daniel McColgan, the Catholic postman shot dead in north Belfast yesterday, has appealed for calm and for no retaliation to the murder.
"We want no retaliation. The only thing we ask is 'Why Daniel?'", the victim's girlfriend said in a statement read to reporters at their Belfast home. The couple have a baby daughter.
Two men are being questioned in connection with the murder.
The gun used had apparently been used in a previous attack on a relative of Sinn Féin Stormont Assembly member Mr Alex Maskey.
Yesterday a statement issued by the Red Hand Defenders - a cover name which has been used in the past both for the UDA and the Loyalist Volunteer Force - said all Catholic postal workers were now considered "legitimate targets".
Senior security sources believe the UDA wa responsible.
The attack followed threats made to teachers and Catholic workers at Catholic schools in north Belfast on Friday.