A post-mortem examination on the body of a former garda confirmed he died from gunshot wounds to his upper body.
Gardai have renewed their appeal for witnesses following the murder of John Kerins, whose body was discovered in his remote rural home on Friday at around midday.
Officers were still at the scene of the large two-storey house in Cornaveagh, near Bailieborough, Co Cavan, carrying out forensic examinations.
"Gardai investigating the murder of John Kerins can confirm that the post-mortem was completed at 12.45pm today," said a spokesman. "He received gunshot wounds to his upper body."
It is understood the victim, in his late 40s, had been questioned over his neighbour's disappearance 18 months ago.
Mr Kerins, who served in a number of specialist units in An Garda Siochana throughout his career, had been medically discharged several years ago and moved to the area. He was arrested and questioned by gardai when his neighbour Gerard Daly vanished in June 2010.
The missing man, a dog breeder from Dublin, is feared murdered.
The pair were said to be planning to go into a security dog breeding business together before Mr Daly's disappearance. Mr Kerins was also recently arrested and questioned over the seizure of stolen goods.
The father-of-one separated from his wife last year and was living alone at the house which is 7km from Bailieborough off the main road to Cootehill. He was said to have become dishevelled over the last 18 months, growing his hair and beard long.
It is understood his body was found by a member of his family.