Forty-four-year-old Steven Kirkwood stabbed Michael four times and he died from massive blood loss.
Michael’s niece, Haylie O’Hanlon, said: “Steven Kirkwood is an evil man. I hope he rots in jail for the rest of his life.”
The brutal knife attack took place in the office of HK Autotek garage in Stevenson, Ayrshire, on 25 July last year.
Kirkwood was originally charged with murder, but the jury at the High Court in Glasgow unanimously convicted him of the reduced charge of culpable homicide under provocation.
The court heard that the killing was sparked by abusive emails sent by Kirkwood and his former partner Eileen Kirkwood, who was due to marry Michael.
Judge Lady Rae told Kirkwood: “The background to this incident appears to have been an exchange of the most insulting and abusive communications between you and your former partner. Each participant was, in my view, as bad as the other and it is frankly astonishing to see adults behaving in this way.
“The consequences were tragic leading to the death of a much-loved man.
“What is clear is you challenged Mr O’Hanlon to fight. You set the place and the time. You then went armed with a lethal weapon.
“You were armed and in the course of the fight between you and Mr O’Hanlon, which lasted no more than 30 to 60 seconds, you stabbed the deceased four times causing very serious and fatal injuries.
“You now, I am told, express some regret for the killing, although somewhat belatedly I suspect that regret is directed more towards your predicament rather than real remorse for what you did. As you gave evidence I detected no remorse whatsoever for causing the death of another human being - you seemed intent on placing the blame on everyone else rather than yourself.”
Speaking outside court afterwards, Miss O’Hanlon added: “He’s nothing but an evil man, he’s always been evil. Any Human Rights should be wiped away from him.
“He’s an arrogant man. He just sat there shaking his head.”
Michael’s sister Janice O’Hanlon said: “Michael never sent any of those texts. Michael was a big softy. Body-building was his life and if Steven Kirkwood hadn’t killed him he would still be competing.
“It chilled me to the bone listening to what he did to Michael.”
Michael’s fiancee Eileen Kirkwood – who has changed her name by deed poll to O’Hanlon – was not in court to see Kirkwood sentenced.
Kirkwood claimed that he had acted in self defence after being assaulted by 45-year-old Michael, from Irvine, and his friend Forbes Cowan, 52, a former competitor in the World’s Strongest Man contest.
His QC Derek Ogg said: “Mr Kirkwood has expressed empathy and remorse.”
As Kirkwood was led away to begin his sentence he mouthed to his partner Martine Greenan: “I love you. I’m sorry.”
The court heard Kirkwood had issued a Facebook challenge to 45-year-old Michael, from Irvine.
In evidence Eileen O’Hanlon said that as the date of her marriage approached, she and Michael began to get abusive texts from Kirkwood. She admitted that she also sent vile texts making comments about Kirkwood’s new partner.
Ms O’Hanlon said: “Michael gave me a kiss and a cuddle and said, ‘I won’t be long’.
Garage owner Ian Hamilton, 40, from Saltcoats, told the court that he saw Kirkwood with a large Rambo-style knife.
Kirkwood denied taking the knife with him and claimed he picked it up from the office floor in the garage as he was being assaulted by Michael and Mr Cowan.
Mr Hamilton said that as he sat in the office having his lunch around middday, Kirkwood walked in.
About a minute later Michael, who was 6ft and weighed 17 stone, turned up with 6ft 4in Mr Cowan
Mr Hamilton said: “Mr Cowan entered the office first and requested for Mr Kirkwood to come outside. There were heated words exchanged between the two of them and Mr Cowan attempted to remove Mr Kirkwood.
“Mr Kirkwood told him, ‘It’s got f*** all to do with you. It’s to do with his f***ing stupid bird’.
“Michael charged through the door with his head down and came at Steven. They tussled, it was a scrummage. It was a wrestle for five seconds.
“Michael backed up out the office stumbling backwards. At that point I saw Steven had a knife in his right hand.
“I saw blood on the entrance door to the office. I saw blood on the knife.”
When Mr Hamilton went outside he saw Michael lying on the ground outside badly injured.
Mr Cowan described Kirkwood as “aggressive” and said it looked as if he and Michael were punching each other.
He said Michael left the office first and he saw Kirkwood had a knife in his right hand.
Mr Cowan added: “Michael wasn’t in a good state. I was speaking to him and keeping a eye on Steven Kirkwood who was still holding the knife. He just stood looking at Michael for three or four minutes then he left the office and walked out.”
Forty-five minutes later Kirkwood confessed that he had stabbed Michael and added: I think I’ve killed him.”
In evidence, Kirkwood admitted he had stabbed Michael, but claimed he was acting in self defence.
He said that Mr Cowan and Michael were raining blows down on him and said he found a knife and swung it behind him.
Kirkwood added: “When I left the garage I didn’t know what had happened.
“Musk was having breathing difficulties. I didn’t think I had struck Musk with the knife.”