A mobile phone clip showing a man being punched to the ground was shared thousands of times on Facebook – just days before the victim died.
It shows two men squaring up to one another in a housing estate in Co Antrim before one throws a punch.
The punch connected with the jaw of Andrew Donaldson (right) who was knocked off his feet before falling heavily to the ground.
He did not return to his feet in the duration of the clip.
Shortly after the video was taken it was uploaded to Facebook where it was shared up to 10,000 times. Alongside the video, dozens of people posted mocking messages regarding the victim while others praised the attacker.
The 24-second clip was filmed at Rocavan Meadows in Broughshane, near Ballymena on September, 19.
It has emerged Mr Donaldson (31) subsequently passed away in London.
The PSNI yesterday said it was unable to confirm the date of his death but the Belfast Telegraph understands he lost his life on Monday. A police spokeswoman confirmed a 33-year-old man was arrested on Tuesday for alleged serious assault.
The suspect was detained a short distance from where the video clip was taken and escorted to Ballymena Police Station for questioning.
He was released on bail pending further inquiries.
The cause of Mr Donaldson's death is still being investigated and police are awaiting the results of a post-mortem examination. Officers from the PSNI are working with colleagues in the Metropolitan police, the force leading the inquiry.
The family of Mr Donaldson, who was engaged to be married, were too distressed to comment yesterday.
However, his sister posted a poignant poem on her Facebook site along with messages thanking friends for their support in recent days. "There's a numbness throughout my body, yet pain beyond belief," she posted.
"I never imagined a person could feel such searing grief.
"I have no idea how I'm going to cope without you, how I'm going to carry on,
"But I hope from heaven you will give me the strength to be strong."
Police have appealed for anybody with information regarding the incident to contact detectives at Ballymena on 0845 600 8000 or pass details on anonymously by calling the Crimestoppers charity on 0800 555 111.