Mr Tupuola put the knife on the far side of the kitchen.
"He looked back and saw the accused take a couple of steps towards the kitchen bench.
"He saw him pick up the knife, walk across the kitchen where he stood over John Chambers - who was still sitting in his seat - and in one quick motion, lunge downward and stab him in the chest."
Mr Glubb said Mr Chambers stood up and staggered down the hallway before collapsing.
"In one fell swoop, he had stabbed him directly in the heart. He effectively and very rapidly, bled out on to the floor."
Police and ambulance arrived 10 minutes later.
"Sadly, even by then, it was too late and John Chambers was dead where he lay in the corridor."
Mr Glubb told the court that two other residents saw Olley scale the side of the boarding house.
He said Olley phoned and sent text messages to friends for help. His friend Martin Charles Bush later picked him up from Wyndham St, near St Patrick's Cathedral in the city.
Mr Glubb said Olley told Bush that he had stabbed another man and that someone was dead.
Bush took Olley to a house on the North Shore and the next day Bush's sister, Ashleigh Bush, picked him up and took him to another house.
Martin Bush has been charged with accessary to murder, and his sister Ashleigh has been charged with being an accessory after the fact.
They too have pleaded not guilty.
The trial is set down for two weeks and will hear from 53 witnesses.
