Non-profit crime-fighting organisation the Heritage Protection Group (HPG) claimed Naude was shot dead by a man who pulled up alongside him when he stopped his car near Mokopane after it overheated.
Police spokesperson Lieutenant colonel Mamphaswa Seabi said officers found his body after being called to the scene.
He said: "The man was lying with his face up and there was blood on his head and face."
The HPG also claimed two men had stepped out of the truck before one person shot him.
One of the men also stole one of Naude's pistols before fleeing.
A local cattle herder backed up claims, saying they heard a gunshot before seeing the two men in a white Nissan truck speeding away.
Naude's Pro Hunt Africa company, located in northernmost South Africa, describes itself as a "hunting and Eco Safari outfit".
