John O’Donoghue, aged 62, collapsed and died as he tried to confront two burglars as they ran from his house in Doon on August 27.
The four men arrested yesterday, under organised crime legislation, are all in their 20s and have connections to a drugs gang.
One the men being held is also related to one of the country’s biggest importers of drugs who supplies Limerick’s McCarthy-Dundon gang, and has been linked to two notorious murders by gang members.
The three others arrested also have connections to the McCarthy-Dundons.
They were arrested at houses in the Doon and Pallsagreen areas shortly after 7am in an operation led by Insp Luke Conlon from Bruff Garda Station.
The operation involved more than 40 gardaí and included the Armed Support Unit with other specialist units.
Two men had been apprehended shortly after the burglary at Mr O’Donoghue’s home. Relatives, connected to those arrested, had erected wooden stables at Brooksbridge, near Pallasgreen some weeks ago. They kept sulky horses there which are raced on the nearby N24 Limerick-Tipperary road.
The wooden building, however, was burnt down on September 28 and gardaí reportedly suspect it was an arson attack carried out by a local vigilante group in revenge for the death of Mr O’Donoghue.
Later that day, a hay shed was burned down near Doon and two more hay shed fires were ignited in the same area on October 5 and 6.
Damage to the three farms targeted were estimated at more than €200,000.
Gardaí suspect the hay shed fires were started in revenge for the stables’ fire.
The farmers, whose hay sheds were set alight, are highly respected members of the community, gardaí said.
Three of the men arrested in yesterday’s operation are being held in Garda stations in Limerick and the fourth is being held at a station in Tipperary.