A youth of Satrod Khas village in the district allegedly injured his father's paramour and killed her daughter with a knife at local Shiv Nagar on Wednesday.
Subhash was angry over his father Bijendar Singh's relationship with Saroj. While Saroj is battling for her life in a local hospital, her daughter Manisha succumbed to injuries.
Bijendar Singh was having an illicit relationship with Saroj for the past a few years. Subhash had been objecting to it in the past and had threatened Saroj to end the affair.
After getting the threat, she left the village and settled at Shiv Nagar in Hisar. However, Bijendar Singh continued to meet her.
Earlier, Saroj had reportedly told Subhash to stop his father from visiting her rather than threatening her.
However, Bijendar Singh carried on the relationship. The police have arrested Subhash and recovered a sharp-edged weapon.