The 65-year-old victim, known locally as ‘Nelson’, and his wife, 57, had been driving along the Caddy Road, near Randalstown, on Wednesday when their car was forced off the road.
The couple were then attacked and money from their night’s takings at their Chinese restaurant in Randalstown was stolen.
‘Nelson’ died as a result of multiple stab wounds.
A 30-year-old man has been arrested during the early hours of Friday.
A woman, aged 31, and a 29-year-old man arrested on Thursday remain in custody.
His wife managed to raise the alarm at a nearby house after the attack.
The detective leading the hunt for the murderers, Detective Chief Inspector Eamonn Corrigan said police received a 999 call just after midnight on Thursday.
“The woman had suffered wounds to her hands and head,” he said.
“When police arrived at the scene a short time later, they discovered the body of her husband.”
The woman underwent surgery but her injuries are not thought to be life-threatening.
Mr Corrigan said the couple, who owned a restaurant in Randalstown, had been forced off the road by two other vehicles.
The detective said there was “no suspicion of a hate motivation”.
“I would appeal for information from the public, specifically anyone who saw vehicles moving along Caddy Road between 11.30pm on Wednesday night and 1 pm on Thursday morning.
“I am also interested in speaking with anyone who may have noticed a black Seat Toledo car, registration number OE62 FRF, in the Randalstown area from around 9pm to midnight on Wednesday 7 January.”