Last night a post-mortem examination on the body of journalist and researcher Tom O'Gorman (39) discovered that one of the victim's lungs had been removed in the horrific attack.
Gardai made the gruesome discovery at Mr O'Gorman's home in Beechpark Avenue, Castleknock, Dublin, when the suspect – Italian Saverio Bellante (34) – phoned the emergency services at around 12.50am yesterday.
Originally from Perugia in Italy, Mr Bellante has been living in Ireland for the past two-and-a-half years working for a pharmaceutical company in Dublin.
He had been living in Mr O'Gorman's house as a lodger over the past number of months.
It is understood Mr Bellante, who was described as being "calm", told gardai that he had killed another man. An operator kept him on the line as emergency personnel rushed to the scene.
When officers arrived, they found Mr O'Gorman's badly mutilated body in a pool of blood.
Mr Bellante claimed he killed his victim after a row over a chess move – and then ate his heart.
The suspect, who was arrested at the scene, later told gardai that Mr O'Gorman asked him to leave the house following the row and he agreed to do so.
But Mr O'Gorman, a researcher with the Catholic lobby organisation the Iona Institute, was then stabbed with a kitchen knife a number of times but managed to fight off his assailant. He was then beaten several times over the head with a dumbbell.
There were a number of stab wounds to the body and blunt-force trauma to the head. The chest cavity had been opened with a knife.
Sources revealed that the post-mortem examination was unable to establish if the victim was dead before his body was mutilated.
A source said: "The victim's heart was intact but the post-mortem confirms that a lung was removed from the body and has not been located."
The source added: "The investigation is following a definite line of inquiry."
A single man, Mr O'Gorman was the eldest of three children and had lived with his mother Ann at the house before she passed away in 2012. Last year, he rented a room to Mr Bellante.
The house was sealed off yesterday for forensic examination while gardai questioned the suspect in Blanchardstown station.
Mr O'Gorman has been described as a devout Catholic who worked as a researcher for the conservative Catholic lobby group.
According to the organisation's website, Mr O'Gorman held a BA and MLitt in history from UCD and a diploma in legal studies.
He was a former journalist with The Voice Today and a regular contributor to the Irish Catholic.
The victim was an opponent of abortion and same-sex marriage.
Mr O'Gorman was also a member of the Focolare Movement, an international organisation promoting the ideals of unity and universal brotherhood.
It is understood that Mr Bellante was also a member of the organisation who shared the same conservative Catholic beliefs as his former landlord.
Mr O'Gorman's killing is the fifth violent death in the Republic in the past seven days.