A WITNESS at the unit where Scott Frank Williams died says he's sorry he did not stop a violent argument.
Mr Williams died in Buddina in January 2016.
Brandon John Mischewski has pleaded not guilty to unlawfully killing him.
Mr Mischewski also pleaded not guilty this week to unlawful striking causing Mr Williams's death.
The Crown has claimed Mr Williams was a homeless drug addict who died after suffering a large fracture to the left side of his skull.
On Thursday, Richard Ratima told jurors at Brisbane Supreme Court he observed both men throwing punches on January 24.
"Frankie” died the next day.
"They walked in and had words. It was on. It happened that quickly,” Mr Ratima said.
"In hindsight, I should've stopped it. It's unfortunate that I didn't.”
Mr Ratima said he was "shocked” at the outbreak of violence.
"All I remember is Frankie lost his feet, slipped up, hit his head.”
Mr Williams was lying on the ground, the witness said.
"It looked like he was hurt.”
Mr Ratima said he and another man picked up Mr Williams and put him on a mattress in a bedroom.
"[We] cleared his airways and within 10, 15 minutes he recovered his consciousness.”
"Frankie was awake and he said he was fine,” Mr Ratima added.
"He was just groggy. I couldn't tell if it was from the drugs he had taken, or if it was from the fall,” Mr Ratima added.
On Wednesday, prosecutor Phil McCarthy claimed Mr Mischewski, after his arrest, told an undercover cop "I punched someone the other day and they died”.
The prosecutor told jurors a dispute over money preceded the fatal incident.
The trial continues. -NewsRegional