Swarn Kaur (75) and her daughter Balbir Kaur (48) were smothered to death by Darshan Singh in their Rajouri Garden house on November 6 and later he set the bodies on fire, police said.
The accused fled immediately from the spot along with some ornaments.
"We zeroed in on Darshan Singh during investigations. He told us that he has been serving as a sewadar in a Gurudwara in Subhash Nagar. He became close with the family through Kaur's sons. He developed intimacy with the family on the pretext of bringing a marriage proposal for one of the sons, police said.
"He started visiting the house. On the day, he asked for some money as loan from Swarn Kaur. He demanded Rs 2000. Kaur took out currency notes to give him money. He saw there was more money and asked for all the cash but she refused," they said.
Singh then allegedly tried to snatch the currency from Kaur and during the altercation, Kaur caught hold of the beard of the culprit, they said.
"The accused inflicted fist blows on Kaur and when she fell down, he smothered her and killed her. After some time he opened the door as Balbir Kaur was knocking the door and was raising a hue and cry. As soon as Balbir Kaur entered the room he overpowered her and after smothering he killed her also," police said.
After killing both the women, the accused poured mustard oil on both the bodies and also put some polythene papers and set them ablaze, they said.