A was questioned tonight by the PSNI about the murder of a father of six in front of his children in west Belfast earlier this year.
Danny McGurk, 35, was gunned down at his home in the Lower Falls area inAugust.
Police and relatives of the victim blamed republicans opposed to Sinn Féin's peacestrategy.
Mr McGurk, who had no paramilitary links, had been locked in a bitter disputewith a senior member of the Real IRA.
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Three gunmen later called at his Ross Road home and shot him five times.
Several men have been arrested and released by detectives hunting the murdergang.
He is also being quizzed about other serious terrorist offences.
PA