Muniyandi had allegedly murdered 60-year-old Sellammal and her 37-year-old daughter Murugeswari at Melakkal in 2013 following a dispute.
Muniyandi, after being in prison, had come out on bail. When he was on the way to a hospital on a motorcycle at Sholavandan, 20km from here, with his wife and grandson the gang, who came on a bike, hit his motorcycle and pushed him down and hacked him, Nagamalaipudukottai police said.
After severing his head, the gang left it infront of a temple and fled the scene, police said.