Police said Shanmugam, brother of Arumugam's divorced daughter-in-law, confessed that he had murdered the SI as he was responsible for ruining his sister's life.
Arumugam blew up even small problems,and forced his son to divorce her, Shanmugam alleged.
Arumugam was returning home last night when Shanmugam and five others hacked him to death, police said.