A scream from the other end of the phone line may have been the final time Mahmoud Sleiman’s family heard from the young father.

The 24-year-old was last seen on the morning of February 2, 2003, outside his Greystanes home, in Sydney’s west.

Sleiman was seen speaking with a man in a white Jeep Grand Cherokee, which he then entered and was driven away in.

Family members reported him missing later that day after he failed to return home.

That night, they called his mobile phone and heard what they believe was a man screaming before the call was aborted.

In the intervening almost quarter-century of investigations, Sleiman’s body is still yet to be found and no charges have been laid.

Police suspect Sleiman was murdered, with inquiries indicating organised criminals may be to blame.

Information shared with investigators suggested he was involved in disputes with criminal rivals prior to his death.

In the year following his disappearance, investigators scoured bushland in Northmead and sections of the Parramatta River, north-east of his home.

A 2007 coronial inquest concluded Sleiman was deceased and likely died the same day he last stepped out from his family home.

But beyond finding the death was suspicious, the NSW Deputy State Coroner was unable to determine the cause of his death.

Following the inquest, the state’s unsolved homicide unit took carriage of the investigation, which remains ongoing.

NSW Police will issue a fresh appeal for information alongside Sleiman’s partner Jody Swift and son Billy Sleiman on Wednesday.

As part of that appeal, the state government and police force have issued a $1 million reward for information leading to the arrest and conviction of anyone responsible for his disappearance or death.

–AAP