Osmond Roy Greig warned on social media he would see his ex-wife’s new partner “in hell” just minutes before he stabbed the man 86 times.

It was about 11.25pm when Greig broke into the Alexandra Hills home Daryl Corcoran had shared with Greig’s estranged wife for only a few weeks.

He was armed with an axe and two knives.

Just two minutes before Greig had written, “No RIP for Daryl Corcoran” in a Facebook post, adding he would see Corcoran in hell.

Corcoran’s sister read the post, her heart sinking before she tried frantically, but unsuccessfully, to contact her brother.

Greig, 43, pleaded guilty to murder in a Brisbane court on Tuesday over the attack on November 22, 2016.

After using the axe to break a window at the property Greig went to the bedroom where the couple had been sleeping.

There he stabbed Mr Corcoran in the face, throat, abdomen and back in an “anger-filled” attack.

The 37-year-old’s injuries were so extensive an autopsy couldn’t determine if both knives Greig was carrying were used, but most injuries were from the smaller, sharper weapon.

After stabbing Corcoran, Greig turned a knife on himself, cutting his own arms, legs and throat, the Brisbane Supreme Court was told.

It was very clear Greig intended to kill Mr Corcoran, Justice Ann Lyons said.

“You took another man’s life in a violent, sustained, premeditated, planned and anger-filled attack in front of your estranged wife,” she added.

Greig also left “what was essentially a will” in a note in the house.

He had earlier threatened his estranged wife in a “series of texts” intended to frighten her.

“It’s clear from the material before me that it was intended by you to inflict maximum damage to as many people as possible,” the judge told Greig.

She said he had “incredibly” tried to blame his ex-wife for his actions in one Facebook post.

“Mr Greig, I want to make this manifestly clear: You are to be sentenced for your actions and the choices you chose,” she added.

“You knew what you were doing. You planned those actions in advance and carried them out at night to cause maximum surprise.”

Lyons said Corcoran had yelled at his partner and three children to leave the house.

Greig’s estranged wife was able to get the children to leave the home before Greig took the knife to himself in front of her, while the room was already “awash with blood”.

“(She) tried to remove the knife and eventually managed to do so,” the judge said.

But nothing could erase the loss of Corcoran’s life for his family and “their profound and ongoing grief”.

Allison Shorten told the court her “world crashed” and her life changed forever when her brother died.

“That night was the worst night of my life,” she said.

“I saw the Facebook post that was put up by the defendant saying, ‘RIP Daryl Corcoran’ just before he killed him and my heart sunk straight away.”

It was only hours later she found out her brother had been stabbed.

Corcoran’s daughter Shaylee Boske told Greig he had “taken everything” from her.

“You stabbed my dad to death when I was just 20 years old,” she added.

“I did not know how to deal with that. I still needed him so much. I still need him now.”

Boske said her father was “so in love with what his future had in store for him” and was looking forward to life with his new partner.

Lyons sentenced Greig to life imprisonment for murder, saying, “You will forever be serving a sentence of life imprisonment.”

“For the rest of your life you are subject to that sentence.”

Greig will be able to apply for parole after serving 20 years.

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