ACP P Ramana said that Karapati Sudhakar, the accused, went to his father-in-law Venkata Rao's house on the night of November 24 and beat him with a stick.
When Sudhakar's wife Karapati Keerthi -- who was living with her parents after their relations soured -- and her mother woke up and tried to intervene, Sudhakar hit them too, causing both of them severe head injuries.
Hearing the commotion, the neighbours woke up and called an ambulance. All the three were admitted to King George Hospital where Venkata Rao died on November 27.
Sudhakar and Keerthi were married seven years ago and have two sons. But soon after the marriage Sudhakar allegedly began harassing her for more dowry and also suspected her character.
On October 30, he allegedly tried to strangle her. She escaped and went to live with parents.
Sudhakar asked her to return, but she and her parents refused, so he wanted to kill them, police said. Further probe is on.