Harnek Singh, 40, who works in a government college in Amritsar in Punjab, had come to his parents' house in Sector 34 on holiday.
"He took his dog out for a walk at around 10 p.m. (Thursday). A rashly driven car passed them, narrowly missing his dog," a police official said.
Harnek shouted at the occupants in the car, who handled him roughly.
The teacher then went back to the house, took out a revolver and fired in the air. The frightened attackers fled.
Harnek, who was in an inebriated condition, misbehaved with the policemen and refused to accompany them.
"We detained Harnek for questioning. We took him to a hospital for medical test. The weapon was seized," police officer Uday Pal told IANS.
The lecturer's family accused the police of trying to shield the accused and harassing them instead.
Nichattar Singh, father of Harnek, said: "My son fired in self defence. Instead of arresting the culprits, they took Harnek to the police station."