The shooting of a man in Carrickfergus is being linked to a loyalist feud in the area.
Police said a man in his 40s was taken to hospital with life-threatening injuries following the attack in the Woodburn Estate on Monday afternoon.
A major security operation is underway in the area.
Police said the investigation is still at an early stage but added that they are "following significant lines of inquiry".
They added that there will be a continued police presence in the area as officers search for those who carried out the "brutal" attack.
A spokesperson said: “Firearms being discharged in a residential area, particularly during daylight hours when children are in the vicinity, is concerning.
"We need the community to give us the information needed so we can remove the dangerous individuals who carried out this attack from our streets and put them before a court of law."