In a gruesome incident, a 21-year-old man today allegedly stabbed to death four members of his own family including his father in Adarsh Nagar area of the city.

Harmit Singh stabbed to death his 65-year-old father Jai Singh, his 60-year-old wife, their 28-year-old adopted daughter and her three-year-old child with a sharp-edged weapon early this morning, ADG (Law and order) R S Meena said.

Harmit, who is said to be mentally unstable, has been arrested, he said.