Vikas Pawar, the accused, allegedly murdered his grandmother Maini Pawar and another woman called Girija Pawar, who was his 'step-grandmother', at his house in Ganjad-Dasrapada of Dahanu tehsil.
He bashed in their heads, police said. However, what made him commit the grisly crime was not known yet, said the district police PRO Suresh Nirmal.
Further probe was on, he said.