A suspect in the murder of IRA commander Gerard 'Jock' Davison was released by police last night.
Police are probing a number of possible motives for the gangland-style shooting in a south Belfast street this week.
The 27-year-old man was freed unconditionally more than 24 hours after his arrest in Belfast on Wednesday.
He was the second person to be arrested in connection with the murder.
A 41-year-old man held on Wednesday was released unconditionally a few hours later.
Davison was shot as he walked to work in the Markets area of city on Tuesday morning. The 47-year-old community worker was ambushed just after leaving the corner shop where he called each morning to buy a paper. It is believed a lone gunman emerged from an entry and shot him several times in the head and chest before making off on foot.
People close to Davison believe he was murdered because of his anti-drugs stance.
Police have been carrying out door-to-door inquiries in a bid to gather information about the murder, which was carried out in broad daylight.
However, it is understood witnesses have been reluctant to come forward.
Davison was accused of ordering the murder of Belfast man Robert McCartney, who was stabbed to death following an altercation with a number of IRA men in a city centre bar.
Mr McCartney's friend Brendan Devine had his throat slashed during the 2005 attack, which made headlines around the world.
Davison was questioned by police about the killing but was released without charge.
Yesterday Mr McCartney's sisters told the Belfast Telegraph their campaign for justice has now ended after Davison's murder.
"We wanted Jock to face justice in a courtroom, not down the barrel of a gun. But the type of justice we hoped for has eluded us. We will never see Jock standing in the dock now," said Catherine McCartney.
"This man brought death and destruction into our family and into many families across Belfast."
Police investigating Davison's murder have ruled out any sectarian or paramilitary link.
Appealing for information, Detective Chief Inspector Justyn Galloway said: "This was a cold-blooded murder carried out in broad daylight in a residential area and it has no place in the new Northern Ireland.
"We have detectives in the Markets area making house-to-house inquiries and seeking to identify witnesses."