A 16-year-old boy with multiple stab wounds cried out to a neighbour, "he's going to kill me", a Supreme Court jury has heard.
The court heard Wagga Wagga teenager James Boonjune Cleghorn was stabbed more than 30 times and died in a unit below his family home on June 7, 2016.
Bryce Cliff, 30, a former boyfriend of the teen's half sister, has pleaded not guilty to murder in the Wagga Supreme Court.
During his opening address earlier this week, public defender Eric Wilson told the court his client did not deny killing James, but he did not intend to do so.
The court heard the teenager's mother owned two well-known Thai restaurants in the southern New South Wales city.
The jury was on Friday played a video recorded by NSW Police, in which the teen's neighbour, Wade Garland, 31, recounted events on the night the 16-year-old died.
Mr Garland, who lived in a unit below the teenager's family home, told police in the recording that he heard a, "distinctive sound of absolute distress … a bang, bang, bang in quick succession."
"I knew the sound wasn't right," he said.
Mr Garland said that when he left his unit and walked up a front external staircase to investigate the noise, the teenager ran past him and cried out, "he's going to kill me."
Mr Garland said he tried to grab James, but the teen slipped out of his hands, so he continued up to the front door, where there was "blood everywhere."
The court heard that while he was standing outside the front door, Mr Garland saw a man's arm come out of James's home holding a "stabbing implement".
Mr Garland told the court that his dog, who was by his side, lunged at the man who then retreated back inside.
In the video, Mr Garland described hiding under the outdoor stairs, arming himself with his dog's chain.
He told police the man re-emerged from the upstairs unit and "was off his lid".
Mr Garland re-enacted a fight between himself and the man, in which he "summoned everything" and gave him an uppercut under the chin.
He said the man then fled, "like a mad man … running down the street."
Mr Garland said he and his dog gave chase and the man pulled out a hammer before running into the yard of a nearby house.
"He was trying to get away from me," he said.
Mr Garland said he returned to his unit to find it locked and when he forced entry, he found James lying on his back in the kitchen.
Mr Garland said in the recording that he feared the teenager was dead, but asked another neighbour to confirm his suspicions.
The trial is expected to run for more than two weeks.