The family of a McDonald’s manager, who was executed with a shot to the head and found under a Sydney bridge with his hands bound, is still searching for answers after a coroner ruled he was killed by “persons unknown”.

NSW Coroner Les Mabbutt has offered his condolences to the family of 34-year-old Darren Alexander Galea, who was killed in January 2014 at Auburn.

“Tragically, the terrible and shocking impact on his closed-in family has left his loved ones with many questions that can’t be answered,” he said at Glebe Coroners Court on Friday.

Darren Galea’s murder remains a mystery more than four years after his execution. Photo: NSW Police

Mr Galea stopped by a mall to purchase orchid flower bulbs after finishing work at 4pm on January 15.

He was a member of the local orchid growing society and shared his love of the flowers with his father.

He returned home, neatly placed his uniform on a chair and left, with the last confirmed sighting at 8.20pm when Mr Galea was driving his car, the coroner reported.

He then met with people known to him in an unknown location.

Several witnesses heard gunshots near Bangor Park but did not report them to police.

At 2.30am the following morning, residents near Mr Galea’s house heard an explosion, which was his car being set on fire and destroyed.

His body, with a pillow on his head, was subsequently discovered beside the Duck River by a passerby.

The coroner ruled the cause of death as homicide by persons unknown and referred the case to the state’s unsolved homicide unit for further investigation.

Homicide Squad Detective Inspector Mark Henney doesn’t believe Mr Galea was killed out of retribution.

The fast-food restaurant manager had no criminal links and had not been in a relationship since 2012.

Det Insp Henney told the inquest on Friday that Mr Galea had a “very trusting attitude”.

He said there was no evidence money issues he experienced two years before his death could be linked to the murder.

Police at the time received a report the killing could be linked to the sexual assault of a six-year-old girl in a Guildford toilet block, but Det Insp Henney said investigations showed Mr Galea had nothing to do with that.

Mr Galea was the youngest of four sons. His parents migrated to Australia from Malta.

-AAP