Hirya Pandu Parab, who is in his 30s, attacked his father Pandu Parab with a wooden plank yesterday at Dhanore village in Palghar district following which the latter died, Kasa's assistant police inspector Ravindra Magar said.
The accused, who is mentally unstable, was earlier admitted to a hospital for treatment, he said.
The motive behind the killing was yet to be ascertained, he said, adding that the body was sent for post-mortem.
The accused was arrested last evening and booked under section 302 (murder) of the IPC, Magar said.