A killer broke down and sobbed in court while saying "I'm so sorry" to his victim's parents sitting in the public gallery.
Giving evidence for the first time at his murder trial, James Andrew Burton claimed he lost control and "flipped" before stabbing Matthew Dunn 29 times.
Yesterday, Burton (32) wept repeatedly in the dock and said: "It should have been me who died. I was prepared to die, he wasn't.
"If I could bring him back I'd swap places with him. I think about him every day. I think about his son, of his son not having a father.
"I think about his family, his brother, his mum, his dad."
Turning to face Mr Dunn's parents, his face reddened as he said: "I'm so sorry."
Burton, of Parry Close, Earl Shilton, denies murdering Mr Dunn, on the morning of January 24.
The cause of death was a stab to the back of his neck, severing the spinal cord, and a knife wound in his heart.
Burton also denies threatening to kill his own son.
He is claiming diminished responsibility because of his mental state. The stabbing happened in Factory Road, Hinckley, at the home of Burton's ex-girlfriend, Aimee Radley, with whom he had a 14-month-old son.
Miss Radley (24) had started a relationship with Mr Dunn, a plastics worker from Wednesbury, West Midlands, and had stopped Burton from seeing their child since October – which had left him feeling suicidal.
When Burton barged into her kitchen at 8.50am on January 24, he said he unexpectedly found 23-year-old Mr Dunn had just arrived.
He told the jury he had taken a knife, ropes and a noose, makeshift handcuffs and lighter fuel with him. He said he planned to talk to Miss Radley and tie her up if she would not co-operate, before hanging himself in front of her if she refused to let him see his son.
He said: "I was shocked to see Matthew, I wasn't expecting him to be there.
"He started coming at me with his left foot in the air, swinging punches.
"That's when I pulled the knife out. The look he had in his eyes was as if he could kill me.
"I stabbed him in the left arm.
"I thought he was going to back off but he didn't. We were grabbing each other, trying to hit each other, everything happened so quickly.
"It's like a black sort of mist, just in a rage. I just flipped."
He said they ended up in the lounge, fighting on the sofa.
Burton said: "He was trying to grab the knife."
Sobbing, he described a haymaker blow with the knife into the back of Mr Dunn's neck, saying: "That's when he got killed. His body went limp, some of the life drained out of him and he collapsed on top of me. I'll never get that image out of my head."
He said he went upstairs, where Miss Radley had fled with their son.
She was calling for help out of a bedroom window and eventually jumped out, holding the child. She suffered three broken vertebrae and the child escaped with bruising.
Burton said he had told her he was going to hang himself and did not threaten to kill his son, saying: "I love my kid with all my heart."
Among text messages Burton sent to Miss Radley in the weeks before the stabbing was one which read: "I told you I never wanted another man around my son playing daddy."
Burton told the jury he still loved Miss Radley but also said he "hated her" for what she had said in court about him.
Under cross-examination, he said: "If she'd let me see my son this wouldn't have happened.
"I do blame her, she's got blood on her hands just as much as me."
William Harbage QC, prosecuting, accused Burton of showing the jury "fake crocodile tears" and giving rehearsed evidence.
Burton lost his temper, saying: "Do you think I'm some cold-hearted killer?"
Mr Harbage nodded his head, saying: "Yes, Mr Burton."
The court heard that Burton had earlier pleaded guilty to another offence of making a threat to kill and inflicting grievous bodily harm on another person.
The case continues.
