His vehicle was bogged in soft sand along Beechboro Road North.
Police believe the man had been trying to flag down motorists for help when he was hit by one of the vehicles.
He died at the scene despite efforts by police and paramedics to revive him.
Det Sen-Sgt Brian Hunter said he believed the victim was struck whilst on the carriageway and the driver who hit him would have known.
“We believe it was a clear night, and if someone had their headlights on he would have been visible,” he said.
He said it was still unclear why the victim’s car had been bogged.
“We don’t know the circumstances of why he was on the road, we can presume a number of things and one of those possibilities is that he was flagging down a car to assist him.
“What we don’t know is the identity of the other driver in the other vehicle, so we know they didn’t stop at the scene or remain there at the scene until police arrived.
Det Sen-Sgt Hunter said the case was a “whodunnit” and anyone with information should contact Crime Stoppers to help police solve the mystery.
“He’s got a family, and they’re understandably distressed at what’s taken place last night and they really want some answers, as do the police,” he said.
He said police were also investigating reports of a car driving erratically in the area around the time of the incident.
Investigators believe the car that struck the man would have suffered some damage and they are examining debris let behind at the scene to pinpoint what kind of vehicle was involved.
Police have urged for anyone who saw a light metallic blue, late 1970s model Holden HZ tray back ute parked at the side of the road to contact Crime Stoppers on 1800 333 000.
In a separate incident, police say a man’s body has been discovered in a car in a remote part of the Wheatbelt.
The man died after an apparent rollover at Jibberding, about 150km east of Moora.
His body was discovered yesterday morning.
Police say it is unclear when the crash happened.