As Nathan Simon ran out of a bedroom waving a knife handle, his brother staggered behind him with the blade embedded in his head and struck back with a machete.
This is the scenario the Crown laid out for a jury in the High Court at Rotorua today, where 41-year-old Simon went on trial for attempting to murder his younger brother, Darcy Simon, in Rotorua on August 5 last year.
He has pleaded not guilty to that charge and another of wounding Darcy, seven years his junior, with the intention of causing him grievous bodily harm.
Crown prosecutor Ngaroma Tahana said the "brutal and frenzied" stabbing was motivated by Nathan Simon's belief his brother was sleeping with his partner.
In the weeks leading up to the attack, the accused had been agitated and paranoid people were after him, Ms Tahana said.
Shortly before the stabbing, their mother had gone into her kitchen to find the accused kneeling, begging her not to turn on the light.
He then lunged at his partner with an object from a metre box, before running to his brother's home down the street, yelling and swearing as he burst through the front door.
Ms Tahana told the jury they'd hear Darcy's daughter testify of hearing her father screaming as her uncle yelled he was going to kill him.
She would tell of seeing the pair emerge from a bedroom, the accused holding a knife handle, Darcy with the blade in his head.
Ms Tahana outlined how Darcy had retaliated with a machete, hitting his brother in the head before Simon grabbed a butcher's knife, continuing to stab him and leaving Darcy bleeding profusely.
At Rotorua Hospital, police heard Nathan Simon tell staff his brother had tried to poison him, that he was dead, saying he was sorry and crying.
Defence lawyer Moana Dorset called the case tragic, saying family would be giving evidence for and against other family members.
"Keep in mind this: there are two sides to every story and Nathan was stabbed with a machete, suffering head lacerations too, he had 20-plus staples in his skull."
The trial before Justice Sarah Katz is expected to run into next week.