Machete-wielding thugs hacked a father-of-two to death after forcing their way into his home.
The man's partner was badly injured in the attack early yesterday involving four men wearing balaclavas.
Seasoned garda investigators described the incident as one of the most gruesome murders in the country over the past couple of decades.
Last night a large team of detectives and uniformed officers from Cork City division, backed up by specialist units, were seeking a motive for the murder as a massive manhunt widened.
The victim was named as 35-year-old Mikolaj 'Nick' Wilk, who was originally from Poland but had been living in Ireland for several years.
Mr Wilk, his partner Elzbieta and their two children, Anna (9) and Jan (4), lived in the rented bungalow in a quiet residential area at The Bridge House, Maglin, Ballincollig, about 5km outside Cork city.
The attackers, armed with machetes and long knives, broke into the house shortly after 3am and inflicted severe injuries to Mr Wilk's head and almost every part of his body, particularly his arms and hands.
Gardai received a call about the incident at 3.17am and first responders were there in less than five minutes.
They found Mr Wilk conscious but incoherent outside the front door of his home. He was rushed to Cork University Hospital where a medical team fought to save his life, but he was pronounced dead two hours later.
Elzbieta (33) sustained seri- ous injuries to her face and hands and was being treated last night for what were described as non-life-threatening injuries.
More than an hour after the attack, gardai found a BMW car on fire at Iniskenny, Ballinora, Waterfall, about 6km from the murder scene.
It will be forensically examined today for clues to the identity of the killers.
A post-mortem examination on Mr Wilk's body will be carried out by a state pathologist this morning.
Gardai said Mr Wilk was a low-key individual and was not known to be involved in any form of serious crime. Officers are carrying out detailed checks on his background to establish if he had fallen foul of criminals or was under any threats.
They will study his financial records to establish if he had owed money.
"We are looking at every possible avenue to try to find a motive as this was savagery of an awful nature," one senior officer said. The two children and another woman who was also in the house at the time were not harmed.
Gardai removed two vehicles, a Mercedes and a Kia jeep, from outside the bungalow for forensic checks.
Officers are also examining CCTV footage on the route between the scene of the murder and the spot where the BMW was found and are carrying out extensive door to door enquiries. Gardai were told initially that the attackers spoke with Cork accents, but said last night they were keeping an open mind on the identity of the gang.
Investigators said they were particularly anxious to speak to any drivers who might have dash cam footage and had travelled in the Maglin, Ballincollig, Ballinora and Waterfall areas between 2am and 5am yesterday, or anyone who might have seen suspicious or unusual activities in those areas within the previous three days.
They ask anyone with information to contact the murder investigation headquarters at Gurranabraher Garda Station on 021 4946200 or the confidential line (1800 666111).
Speaking yesterday at the scene at Bridge House, Supt, Colm O'Sullivan said: "Mr Wilk has left a family and a wife behind as well as friends in the Polish community and the wider community in Ballin- collig."