A 28-year-old man has been arrested by detectives investigating the murder of Colin Horner in Bangor.
The man was detained on Tuesday evening.
Mr Horner was gunned down in front of his three-year-old son in a crowded supermarket car park on Sunday afternoon.
The 35-year-old was a friend of former South East Antrim UDA boss Geordie Gilmore, who was murdered in Carrickfergus in March.
Police, who believe a total of six bullets were fired during the shooting, have described the killing as “barbaric and reckless”.
They said Mr Horner was "known to police" and confirmed "one line of investigation was ongoing loyalists tensions in Carrickfergus".
A 28yo man has been arrested this evening in relation to the murder of Colin Horner in Bangor on 28/05/17.— Police Service NI (@PoliceServiceNI) May 30, 2017