At least two people were believed to have attacked the man, who was found at a bus stop on St Johns Road on Saturday night.
The 33-year-old was taken to hospital in a critical condition but died in hospital.
Detective Inspector Glenn Baldwin said they wanted to hear from anyone who saw suspicious activity at the bus stop near 69 St Johns Rd, between 9pm and 10pm on Saturday.
"We are keeping an open mind as to what may have happened in the moments before the attack and the events preceding it," Baldwin said.
"The motive for this attack is not yet clear.
"Please do the right thing and contact police."
They especially wanted to hear from motorists who had dashcam footage from the area.
Baldwin said police believed they knew who the victim was and were in contact with his family, but a formal identification had not yet taken place.
A post-mortem would be carried out today.
