Karuppusamy died on the spot in the attack last night, police said.
Police said a Sub-Inspector had come to the village along with Karuppusamy to question his daughter-in-law's father in a case of family feud (the DMK functionary's).
On seeing Karuppusamy, the father and his sons attacked and hacked him to death in the presence of the SI, police said, adding, they then fled.