How dispute over a will led to a Cork murder and two suicides

Letters found after the deaths show one son’s grievance and the other’s sense of foreboding

Knowing that she was terminally ill and might not live long enough to testify at an inquest, Anne O’Sullivan gave a series of video-recorded interviews to gardaí investigating the murder-suicide of three members of her family.

Investigators spent several hours with Ms O’Sullivan (61) in recent months taking statements about October 26th, 2020, when her husband Tadg (59) and younger son, Diarmuid (23) killed her other son, Mark (26), before taking their own lives.

Recently, the Director of Publication Prosecutions directed no prosecution is necessary. An inquest into the three deaths will take place in Mallow towards the end of May.

Ms O’Sullivan, who was diagnosed with a terminal illness in March 2020, returned from surgery in Dublin in mid-October with her son, Mark. Returning to the family home, a disagreement led to them moving to stay instead with cousins nearby.


However, on October 23rd, she interpreted a solicitor’s letter sent by her husband as an olive branch, which led her and Mark to return the family home on the evening of October 25th, even though Mark was much against the idea.

Deterioration in relationship 

In a letter found later by gardaí in his mother’s medicine bag, Mark had chronicled the deterioration in the family’s relationship over the preceding months. Eerily, he expressed concerns that it all might end tragically.

In the end, he was killed in his bunk bed after his father, Tadg and brother, Diarmuid, opened fire from the doorway of a downstairs bedroom at 6.30am with two legally-held .22 rifles licensed to Tadg; one a semi-automatic gun and the other a bolt-action gun.

Ten bullets could have been fired in just five seconds from the semi-automatic .22, while the bolt-action rifle was capable of three shots in 10 to 15 seconds, a firearms expert has told The Irish Times.

The majority of the seven bullets that killed Mark came from the semi-automatic rifle, but forensic tests found DNA traces from both men on both guns so gardaí are unable to say which of them fired which weapon.

Hearing the shooting, Ms O’Sullivan raced downstairs. Realising what was happening, she raced for the door, barefoot and in her nightdress, only to be caught in the yard by her husband and Diarmuid.

They grabbed her mobile phone and Diarmuid smashed it with a sledgehammer before he said to her, “I hope you think the land is worth it now”. She would, they told her, have to live with torment and guilt in the time she had left.

Having told her that they would take their own lives by the fairy fort on the farm, they smashed their own mobiles and the house phone. Neighbours heard shots at about 7.10am.

Ms O’Sullivan was not able to drive away as the two had locked the gates at the end of the farm’s long boreen with new padlocks on Sunday night/Monday morning after she and Mark had returned home.

In the darkness, it took her 30 minutes to cross the fields to reach cousins living 750 metres away. Once the alarm was raid, Kanturk gardaí quickly arrived, Unsure of the threat, they waited and they were soon joined by armed gardaí and aerial support.

Gardaí had been told that the two men had threatened suicide, but they could not take the risk of entering the house as they were not sure if father and son were in the house.

Five hours later, with no response given to a Garda negotiator, armed Emergency Response Unit gardaí equipped with bullet-proof shields forced their way in through the front door, quickly discovering Mark’s body in his bedroom next to the kitchen.

Concerned that two armed men, who had already killed once, were loose, armed detectives were sent to the home of a local solicitor, who had represented Ms O’Sullivan, as they feared the solicitor might be at risk.

Shortly afterwards, the Garda Air Support Unit helicopter spotted two bodies by the fairy fort, each with a single gunshot wound to the head. Gardai are satisfied that each man shot himself rather than one man shooting the other by consent and then shooting himself.

However, ballistic tests suggest that both men used the shorter-barrelled semi-automatic rifle to shoot themselves, suggesting that one man shot himself first, and the second man then took the gun and shot himself.

Inherited farm

An only child, Ms O'Sullivan had inherited the 115-acre holding from her parents, Tim and Mary Cronin. Mr O'Sullivan had married into the farm, but neither he nor either of his sons ever worked the land, which was leased out to neighbouring farmers for tillage for more than 30 years.

Ms O’Sullivan had begun to put her affairs in order from March 2020, after her terminal diagnosis, but gardaí now believe the family’s relations over the future of the farm did not begin to deteriorate seriously until July.

Nevertheless, relations between husband and wife had been strained for years, with Mr O’Sullivan taunting his wife over the suicide of one of her relatives years before, while her relationship with Diarmuid had also been poor.

But it was only in July, after Mr O’Sullivan received a solicitor’s letter on behalf of his wife that he began to believe his wife might seek a barring or protection order, which would see him evicted from the family home.

Gardaí believe that Mr O'Sullivan, a native of Roskeen between Mallow and Kanturk, who worked as a mechanic at Greenhall Motors in Buttevant, became hugely concerned at the stigma the local community would attach to such a move.

This led to fears on the part of Mr O’Sullivan and of Diarmuid that they would be excluded from Ms O’Sullivan’s will, even though if Mr O’Sullivan had outlived his wife and contested any will, he would have been entitled to at least one-third of the estate under the Succession Act.

In a 12-page letter to his mother that gardaí found strapped with clingfilm to his thigh, Diarmuid expressed his anger over the inheritance, declaring that she would have to live with the consequences of her decision.

That letter was written before the shooting, perhaps days before. However, it does not mention Mark, which has led gardaí to review their belief that the two men had long planned to kill him. Instead, they may have decided to do so only when they learned he and Ms O’Sullivan were returning.

Besides venting his anger at his mother, Diarmuid left instructions that the family’s two Doberman dogs should be properly looked after.

Greater grievance

The fact that the suicide note found on Tadg was much shorter, at about a page and a half, has also prompted gardaí to question whether perhaps Diarmuid had the greater grievance and may have been the driving force for the killing, with Tadg siding with his younger son.

“Mark could have got a job locally in Kanturk but he wanted away; he had no interest in the farm, whereas Diarmuid had. But Mark was the one who stood by his mother during all her health and medical appointments and it seems she was intent on leaving the farm to him,” said one source.

While the hotly-disputed will had not been actually finalised, it is clear that Ms O’Sullivan planned to divide the farm so that Mark would receive the best quality land and greater share of the 115-acre holding while Diarmuid would be left only a field known as “The Bog Field”.

Diarmuid, who had finished an accountancy degree at Cork Institute of Technology in June 2020, was described as industrious, holding down a part-time job at Burton's Hardware Store in Kanturk as well as setting up a timber delivery business, advertised weekly in The Corkman newspaper.

His mother, Ms O’Sullivan never got to read the letters from either him or her husband as, soon after she expressed a desire to see them, her condition deteriorated. More than two weeks ago she was admitted to Marymount Hospice, where she died on Wednesday.

“In the end, Anne never got to read the two letters,” said one source, “and given the content and the anger that was in them towards her, that was probably for the best; there was nothing in them that would have eased the poor woman’s pain or given her any solace.”

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