Man (27) is held by police over murder of former IRA boss Jock Davison
Second suspect is released without charge
Detectives investigating the shooting of former IRA commander Gerard 'Jock' Davison have arrested a 27-year-old man.
He is currently being held for questioning at a police station in Belfast.
A 41-year-old man arrested on Wednesday morning was released unconditionally last night.
Davison was accused of ordering Robert McCartney's murder in 2005 after he and his friend Brendan Devine got into a bar fight with IRA members.
It is understood that several motives for Davison's murder are currently under consideration.
Police have ruled out a sectarian motive or dissident republican involvement.
However, they are trawling through Davison's past to draw up a list of suspects who may have wanted him dead.
The 47-year-old was quizzed about the high-profile McCartney murder but was later released without charge.
McCartney's sister Catherine claimed in her book Walls Of Silence that Davison had ordered the attack on her brother outside Magennis's Bar in Belfast city centre.
The 33-year-old was stabbed to death, and Devine had his throat slashed after they became involved in an argument with IRA members.
Davison was one of three IRA members expelled following an internal investigation by the organisation in the wake of the killing.
He always denied any involvement in the attack.
While detectives are attempting to determine if Davison's murder is in any way connected with the McCartney case, other motives are also under investigation.
Another theory under consideration is that he may have been murdered as an act of revenge for Catholic father-of-four Samuel Ward, who was shot dead by the IRA in October 1992.
Officers are also probing the possibility that his murder could be connected to a row with drug dealers.
Davison, who had close links to the Sinn Fein leadership, was vocal in his opposition to drugs.
"Over the years Davison had run-ins with all sorts of groups and individuals," a police source said.
A house in north Belfast was searched on Tuesday night as part of the investigation into his murder.
Davison, who was a senior IRA member in the 1990s, was gunned down in a residential street yards from his home in the Markets area of south Belfast as he walked to work.
He worked for the Markets Community Association. He was ambushed by a lone gunman, who shot him several times, before making off on foot.
The father-of-three died at the scene.
It is understood he had previously been warned that he was under threat.