A 40-year-old man has been arrested in connection with the murder of a man on Belfast's Shankill Road.
Bobby Moffett, 43, was shot in the face shortly before 1300 BST on Friday.
The police said Mr Moffett, had strong links to the Ulster Volunteer Force, and was well known in loyalist paramilitary circles.
At least two masked gunmen wearing fluorescent jackets shot him at the corner of Conway Street and the Shankill Road.
He died in hospital. Police do not believe the shooting was sectarian.
There is speculation that Mr Moffett may have been involved in a fight with a member of the UVF in recent days - but this may have been a personal dispute rather than anything to do with the organisation.
The attack happened in an area that was crowded with shoppers.
One witness said: "I heard about four shots and saw the gunmen standing in the middle of the road wearing balaclavas and orange tops.
He said he saw the victim lying on the ground.
"I think he was shot in the head or the face," he said.
Police said it was "a cold-blooded, ruthless killing carried out on a 44-year-old man in the community where he lived".
In a statement, the PSNI said: "It is a chilling reminder of a violent past that everyone in the community hoped we had left behind.
"Police are following a number of definite lines of enquiry and will work with determination and professionalism to catch the killers."
Ulster Unionist Party member Bill Manwaring who works for a homeless charity which has a hostel near the scene of the shooting, arrived moments after it happened.
He tried to offer first aid to the man who had suffered severe facial and hand injuries.
"By the time I had arrived, it had already happened. Some colleagues were helping put him in the recovery position.
"Young children were on the street when this happened," he said.
"We had 40 years of this area suffering from this kind of activity and there is no reason for this. It is unacceptable."
The gunmen were seen running off through nearby Conway Street.
Local clergyman Pastor Jack McKee said witnesses to the attack appealed to the gunmen to stop.
"There were many women and children screaming, weeping.
"And even some that were very close to the murder appealing to the men, as they stood over the body of the person, and just continued to fire bullets into his body.
"And those appeals sadly weren't heeded and the man was shot dead in cold blood in front of a lot of witnesses."
NI Secretary Owen Paterson said that the killer must be caught and brought to justice.
"To murder this man was an evil act but to do it in the middle of the day, on a busy road full of local people going about their normal business only adds to the horror and the sense of shock and revulsion," he said.
"Anyone who could carry out such a barbaric act is a threat to the whole community".
DUP MP for North Belfast Nigel Dodds said: "Everyone will have been shocked and horrified by this incident where someone has been murdered in broad daylight.
"No-one has the right to take the life of another human being and we all want to ensure that Northern Ireland continues to move away from times when reports such as this were all too common."
Mr Dodds urged anyone who had seen anything to contact the police.
SDLP MLA Alex Attwood said the shooting had happened "in broad daylight in front of local people."
"The people will be traumatised and we have to express our sympathy and urge people to keep calm and not rush to judgment," he said.
Sinn Fein MLA Paul Maskey said: "Whatever the circumstances surrounding this shooting or whoever was involved in it, this should not have happened and it is now crucial that the PSNI are given every assistance from the community in that area to apprehend those responsible.
Justice Minister David Ford condemned the killing.
"This cold-blooded murder in broad daylight will shock people across Northern Ireland. Those who carried out this killing are to be condemned and anyone with any information should bring it to the police," he said.