The incident took place on the Kiratpur-Manali road when a car ferrying six policemen from Gurgaon to Kullu skipped a toll-booth barrier without paying the fee, police said.
The booth's employees stopped the vehicle by putting up a barricade, they said.
The cops allegedly abused the employees which led to a scuffle between them, police said.
"One of the policemen opened fire, injuring one Ranvir. He was rushed to a hospital in Nalagarh from where doctors referred him to the PGI hospital in Chandigarh," a police source said.
"The cop who fired with his service revolver at Ranvir is yet to be identified," he said.