Vanamamalai of Maruthal Kurichi, 30 km from here, died on the spot after Nanguneri Inspector Vijaykumar opened fire at him with his service weapon, they said.
Police said the man's younger brother is a historysheeter facing several cases of robbery and attempt to murder and the Inspector had been taking steps to detain him under the stringent Goondas Act.
Vanamamalai entered into an heated argument with the inspector, on a routine visit to the village, over the latter's efforts to book his brother under the Goondas Act when two of his associates came armed with sickles.
When the inspector asked them to drop the weapons, the three allegedly attempted to attack him, following which he fired at Vanamamalai, police said.
The incident sparked tension in the village and the residents resorted to a roadblockade demanding action against the Inspector.
Tirunelveli Range DIG Varadarajulu, District Superintendent of Police Vijeyendra Bidari and Sub-Collector Rohini Ramdoss rushed to the village and persuaded the agitators to disperse.