On Wednesday night, Raibhole went to meet Bahulekar when she was alone.
He had hidden the hammer beneath his shirt and hit her head from behind while she was watching television. He then hit her on her face and left her in the bathroom and fled with the necklace.
KP Raghuvanshi, commissioner of police, Thane city, said "Raibhole said that Bahulekar's son-in-law, Paresh, had plotted the murder with him. We are investigating this."