Thomas, then 18-years-old, and his 16-year-old girlfriend was sitting in his HQ Holden Sedan at Ricketts Point on the night of 18 August.
About 7:15pm a man wearing a hat approached the vehicle and smashed the driver’s side window.
Thomas attempted to drive away, however, the man shot him a number of times.
His girlfriend was able to steer the car away from the area and was not physically injured.
The area was a well-known spot for couples to go ‘parking’ and Thomas and his girlfriend went there several times a week.
Homicide Squad detectives have conducted exhaustive enquiries into the murder over the past 40 years and are hopeful today’s reward announcement will assist with solving the case.
The case has also been reviewed a number of times by detectives.
Previously a $50,000 reward was on offer for information leading to the conviction of the person responsible.
Officer in charge of the Homicide Squad, Detective Inspector Dean Thomas, said the motivation for the murder remained unclear.
“There are a number of possibilities, including that the shooting was sexually motivated and the girl in the car may have been the target,” Det.Insp. Thomas said.
“We know that many couples regularly went to this location so the offender may have been stalking the area in the lead up to the shooting.
“Police have spoken to a number of people over the years in relation to Thomas’ murder, however, we are absolutely keeping an open mind with regards to this case.
“There is no one answer to this that we’re focusing on.
“The one thing we do know is that someone out there will know who is responsible for shooting Thomas and we’re hopeful that after four decades, this person is ready to come forward and assist us with bring his family some justice.”
At the time of Thomas’ murder, police released a digital composite image of a man they wished to speak to in relation to the incident.
Police are also considering whether the offender wore a hat on the night as a disguise.
Detective Inspector Thomas said detectives are keen to hear from anyone who can provide information regarding the identity of the man shown in those images.
“I want people to consider whether these digital images show a person they know or can identify for us,” he said.
“That person may not necessarily be from the Beaumaris or Ricketts Point area and they may not necessarily have regularly worn a hat.
“We’re hopeful that there is someone out there who can tell us who this person is, or has other information about the murder.
“Thomas’s family have had to go 40 years without the answer to who would want to kill their son and brother.
“As we always say, a lot can change over the years and hopefully this reward and the passage of time will encourage someone to come forward and give his family some peace.”
A reward of up to $1 million will be paid at the discretion of the Chief Commissioner of Police for information leading to the apprehension and subsequent conviction of the person or persons responsible for the murder.
In appropriate cases, the Director of Public Prosecutions may consider, according to established guidelines, the granting of indemnification from prosecution to any person who provides information as to the identity of the principal offender or offenders in this matter.