Jeffrey Lawrence Brooks, 24, was found dead with a single shotgun wound to the upper chest at 3.30pm on March 13, 1996 near crayfish ponds on the property where he worked as an aquaculturist at Beenleigh, south of Brisbane.

Following a second inquest into the death in November, coroner Donald MacKenzie handed down his findings on Tuesday that Brooks died after being shot via accidental discharge or by person or persons unknown.

“Having considered the vast array of material gathered over the past 26 years, there is sufficient information to found a reasonable suspicion that Mr Johannes Wolfgang Hans Geiger and Ms Regine Kjellerup were involved in the unlawful killing of Jeffrey Brooks,” MacKenzie said.

Mackenzie said the finding was based on Brook’s past statements that he was in fear of his life, motive, opportunity and behaviour before and after shooting potentially incriminated Geiger and Kjellerup, but he was not stating they were guilty of anything.

There were gasps from the public gallery as Mackenzie read out the finding and said he would refer the brief of evidence to the Director of Public Prosecutions.

Mackenzie did not find any suspicion of crayfish farm worker Graeme Lloyd, who discovered Brooks’ body and called police, as he was an “honest witness”.

MacKenzie rejected much of the criticism of the original police investigation, finding it was adequate and thorough, and gave little weight to privately funded firearms experiments that claimed to have proven Brooks was shot from too far a distance to be an accident.

The 1998 inquest found that Brooks likely died from the shotgun accidentally discharging when Brooks grabbed it by the barrel, and MacKenzie said on Tuesday he could not rule this out as the cause of death.

MacKenzie said Brooks’ parents, Lawrence and Wendy, must be disappointed that the inquest did not uncover new evidence regarding the death of their son given memories had faded and some witnesses were no longer available.

“I can assure them that every avenue of inquiry was pursued … I pass on my condolences of this court for their loss of a fine young man taken too soon,” MacKenzie said.

Lawrence and Wendy Brooks said they were thankful for the coroner referring two potential suspects to prosecutors 27 years after their son’s death.

But they also said they were “really disappointed” that the second inquest did not make adverse findings about the quality of the original police investigation.

“There needs to be an independent body set up in the Queensland Police Service as there seems to be much left to be desired in the way they conduct their investigations,” Lawrence Brooks said.

Wendy Brooks said “it almost went over” their heads when they heard the coroner find their son may have been unlawfully killed after the couple had spent decades challenging the police’s original conclusion that his death was accidental.

“After all this time (the coroner) felt the same way we did … that part was what we were looking for,” she said.