Hindu extremists had threatened Pastor Sankar in the past for preaching Christianity, and had also threatened to kill him.
“The Christians in this area have been facing intense opposition from the radical Hindu nationalists. Several times Pastor Shankar defended Christians from radical Hindu nationalists, and that could be the reason for this extreme form of persecution [through] killing,” a local Christian said.
https://iamc.com/hindu-extremists-stab-christian-pastor-to-death-for-preaching-christianity/