A note running to up to a dozen pages was discovered on the body of Diarmuid O'Sullivan, the 23-year-old student who was found dead alongside his father in a field at their farm near Kanturk on Monday.
Gardaí investigating the suspected murder-suicide are looking at the possibility that the fatal shooting of Mark O'Sullivan may have been planned by his younger brother and father over a period of time.
The body of the 26-year-old trainee solicitor was found with gunshot wounds in the bedroom of the family home at a 115-acre farm at Assolas, near Kanturk, on Monday.
The bodies of his 59-year-old father Tadg and brother Diarmuid were found a short time later near a ringfort half a kilometre from the farmhouse.
The note found on Diarmuid's body is described as lengthy and detailed.
Gardaí said today that the post mortem examinations on all three of the men have now been completed and the results have been given to the investigation team.
Details of the post mortem results are not being disclosed and a file will now be prepared for the Director of Public Prosecutions and the Coroner.
Formal identification of all three bodies by a close friend of the family is expected to take place this afternoon.
Two rifles found close to the bodies of Tadg and Diarmuid were sent to Dublin for ballistic examination.
Gardaí hope that the results of that, along with the post-mortem examination results, will help clarify the exact sequence of what happened to the three men.
The alarm was raised after Ann O'Sullivan fled the farm at 6.40am on Monday morning telling neighbours that her son Mark had been shot.
Neighbours told gardaí responding to the emergency call that they had heard a number of further gunshots.
The bodies of the three men were found five hours later following a Garda Critical Firearms operation involving up to 100 personnel.
Gardaí are investigating whether the suspected murder-suicide may have been triggered by a dispute over a proposed will.
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