A man shot dead in Belfast was a suspect in the murder of a 17-year-old in the Republic of Ireland earlier this year, the BBC understands.
The man was fatally shot outside a house on Etna Drive in Ardoyne at about 11:50 BST on Saturday.
Four men have been arrested in connection with the killing, which police described as "brutal".
It is understood the dead man was a senior figure in a feuding criminal gang.
He was a suspect for the abduction and murder of Drogheda teenager Keane Mulready-Woods whose dismembered remains were found in Dublin in January.
Earlier on Saturday, Det Supt Jason Murphy condemned the Belfast killing and said the man had been shot a number of times at close range.
"Those involved in this murder selfishly gave no thought to the impact on frontline emergency services who are already working hard to keep people safe with an already stretched resource," he added.
"Not only did they carry out this callous murder leaving a family experiencing their worst nightmare, but they did not care that children and other members of this north Belfast community were placed at risk."
Mr Murphy said that a light coloured car, registration YLZ 7052, was found burned out in nearby Kingston Court, and he was trying to establish if this is relevant to the murder.
He also appealed for information about a dark-coloured car which was seen in Ardoyne Avenue minutes after the other car was set on fire.
Neighbours described how they tried to save the man.
One man said he "heard four big bangs and ran outside to see what was happening".
He said he saw a man "stumbling out of the garden" and that he ran over to help but the man collapsed.
"I tried doing CPR but I couldn't save him," he said.
Another witness said she ran to help but that the man was already dead so she put a sheet over him to "give him some dignity".
The killing was condemned by Justice Minister Naomi Long, SDLP councillor Paul McCusker and Sinn Féin MLA Gerry Kelly.