A Rockingham City Shopping Centre car park was turned into a crime scene after a man was found unconscious and another seriously injured on Tuesday.
Police said the two males were found with significant injuries in the car park bounded by Syren Street and Contest Perade about 9:15pm.
A witness statement lead police to believe the pair had been involved in a suspected hit-and-run.
As a result, officers and detectives cordoned off the area for over an hour as they worked to piece together exactly what happened.
Nearby workers and shoppers were unable to access their vehicles as the area was deemed a crime scene.
Police said after reviewing CCTV it was determined the incident was not a hit-and-run as originally suspected.
Police believe three men were involved in a physical altercation.
One man received facial injuries while the other receive head injuries. Both were taken to Royal Perth Hospital for treatment.
The third man remained at the scene with officers.
Police said no charges were to be laid at this time.
The scene has since been cleared and members of the public can now access their vehicles.
The investigation is ongoing and anyone with information should contact Crime Stoppers on 1800 333 000.