Two men who were forced to lure their friend Paul Quinn to his death were interviewed by gardaí last night.
The men, who were injured in the incident, fled the scene of the attack in Co Monaghan and drove themselves to a hospital in Newry, Co Down.
Senior gardaí said the attack was the worst the force has investigated for several years.
"The victim had sickening injuries - it was a sustained savage attack by a group, all of whom had weapons," said one Garda source.
Another said the investigating team were working on the theory that the gang behind the attack most likely meant to badly injure rather than kill Mr Quinn.
The victim was able to talk to gardaí and an ambulance crew that arrived at the crime scene at Tullycoora, near Oram village, Co Monaghan, at about 6pm on Saturday.
It appeared at first that his injuries were not life threatening and consisted of broken bones and severe cuts and bruising. However, as Mr Quinn was being taken by ambulance to Our Lady Of Lourdes Hospital, Drogheda, his condition began to worsen.
He lost consciousness and while he clung to life for over an hour at the hospital, he was pronounced dead at about 8pm.
The precise cause of death was not known last night. A postmortem examination is due to be completed this morning.
The farm where the beating took place is believed to have been used in the past by those engaged in oil laundering. However, this activity has taken place without the knowledge of the farm owners.
In recent weeks Mr Quinn's activities around the area came to the attention of gardaí. Detectives believe he was working with an Armagh-based crime gang which was laundering green diesel in the Republic and selling it as regular fuel in the North.
An oil tanker vehicle which was being used by the gang has been recovered close to the farm near Oram.
Mr Quinn had driven to the farm with a friend in his van, after being contacted by his two other friends via mobile phone late on Saturday afternoon. The two friends, aged 21 and 25, were neighbours of Mr Quinn in Cullyhanna, south Armagh, and were leasing the farm from the owners.
However, when Mr Quinn arrived at the farm and went to meet his two friends in a shed, he was confronted by up to 10 armed and masked men. He was separated from his two friends, who had already been tied up and beaten, and from a third man with whom he had travelled to the farm.
He was taken to another outhouse and subjected to the so-called punishment beating.
The gang then left and told Mr Quinn and the three others to wait for 30 minutes before calling the emergency services. After an ambulance was called, the two men who were tied up decided to leave the scene.
They later arrived at Daisyhill Hospital, Newry, where they underwent medical treatment. They have since been discharged.
The scene of the killing was sealed off yesterday as gardaí carried out a forensic examination.
Gardaí in Castleblayney have appealed for anyone who was in the area on Saturday afternoon or early evening to come forward.
Garda Supt Karl Heller of Carrickmacross, said: "It is too early yet to say what the motive behind this attack may have been, as our investigations are ongoing."
Gardaí in Castleblayney can be contacted on (042) 974 0668.