A fare-beater went berserk and opened fire on three MTA employees who booted from a bus in Brooklyn Tuesday morning, leaving one of the workers with a graze wound to the leg, police said.

The gunman boarded the B82 bus at the corner of Flatlands and Louisiana avenues in Canarsie around 6:20 a.m., but did not pay for the fare, authorities said. 

MTA inspectors were checking for passengers’ receipts on board the bus when they realized the suspect didn’t have one – so they asked him to leave and pay for the ride, cops and sources said. 

He got off the bus and walked down the block — before allegedly opening fire on the three inspectors.

One of the workers went to the Kings County Hospital Center for pain in his arm and elbow, and doctors there discovered his leg had also been grazed by a bullet, police sources said.

The shooter fled, cops said. 

No arrests have been made, though police said they obtained surveillance video from the bus and were working to identify the suspect.

Shell casings from a .45 caliber weapon were recovered at the scene, according to the sources.

The bus had driven away from the scene when the gunman opened fire, police said.

The MTA deferred to the NYPD when reached for comment.

Additional reporting by Nolan Hicks