Police want to hear from anyone who saw a motorist threaten a motorcyclist with a gun west of Yatala on Wednesday morning.
The confrontation occurred on Chambers Flat Road in Chambers Flat.
It is alleged that a driver tried to force the motorbike off the road at 10:30am before showing him a handgun.
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The vehicle is described as a metallic grey Holden Commodore sedan.
Police would like to hear from anyone who was travelling on Chambers Flat Road on Wednesday morning who may have seen the incident or the vehicle.
They would also like to have a look at dash cam footage from around the time of the incident to contact Crime Stoppers on 1800 333 000 or Logan Criminal Investigation Branch.