A man has been found guilty of the calculated and brutal murder of a convicted killer. Eric James Forrest was convicted after shooting the man three times, forcing his body into a tree, and setting it alight.

Forrest will face sentencing hearings in February, as he now joins the ranks of convicted murderers. His victim had previously been jailed for 20 years for a murder committed during a botched robbery in 2000.

The case dates back to when Shahab Kargarian and his girlfriend were enjoying takeaway food at a park on Sydney’s north shore. During the incident, Collisson, along with an accomplice, approached the 17-year-old and demanded his wallet.

In a tragic turn of events, the robbery escalated, leading Collisson to shoot Shahab multiple times, ultimately resulting in the teenager’s death.

Collisson then shot Shahab four to five times in a robbery gone wrong.

Forrest’s trial was told when faced with death on the Mudgee property, Collisson made a desperate appeal to his killer’s humanity.

Prosecutors told jurors the victim drove to the country a day earlier to collect goods to sell, but was killed after 9.12pm the next night on a secluded hill.

Forrest pulled out a sawn-off shotgun and pointed it at Collisson, saying forcefully “you want to treat me like a gronk”.

“The Crown case is that the accused was angry about something – precisely what is not known,” crown prosecutor Emma Blizard told the jury in early October.

She said Collisson pleaded with the younger man, telling him “please don’t, I’ve got kids” and “I love you Eric, like, you’re my brother” before he was shot in the neck or shoulder.

He tried to run away, but Forrest reloaded the gun and shot him twice more, Blizard said.

Collisson’s body was moved into a large hollow tree stump and burned, the jury heard.

Bone fragments – including 17 teeth – were found inside the tree.

Forrest’s lawyer cast doubt on the prosecution witnesses’ evidence, saying they had used ice, which could have affected what they were able to tell the court.

One eyewitness had also received a reduction in his sentence for criminal matters in exchange for his assistance with the three-week trial, Justine Hopper said.

Jurors spent almost a week deliberating before returning a guilty verdict to murder about 11.25am today.

In November 2023, the then-homicide commander of NSW Police said Collisson had been killed in cold blood in a brutal fashion.

“You can only call it callous and cold-blooded, the way he’s been killed,” Detective Superintendent Danny Doherty said.

Forrest will return to court on February 27 for sentencing submissions and will be sentenced at a later date.