Enraged Kumaraswamy attacked her with an axe on the head, killing her on the spot, police said.
When his mother-in-law Laxmi (65) tried to intervene, she was also hit with the axe, injuring her seriously following which she was admitted to a government hospital in a critical condition, they said.
Shocked to see both the women in a pool of blood, the accused consumed insecticide to end his life.
He has been hospitalised and his condition is reported to be stable, police said.
A case has been registered and investigations are on, they added.