The incident took place last night in Mayuresh building when Subhash Wankhede (65), his wife Promodhini (55) and son Dnyaneshwar (25) tried to resist the robbers, who fled with the valuables, they said.
While the couple was strangulated, their son died after the robbers shoved the LPG cylinder pipe into his mouth, resulting in his death due to suffocation, police said.
The couple's daughter claimed that her family could have been saved had the Bazarpeth Police rushed to their aid as soon as they got an alert from the control room.
She told the police that Dnyaneshwar had called her at 8.25 pm to inform her about the robbery following which he called the Thane Police control room, which, in turn, alerted the Kalyan control room but it did not act swiftly.
When the daughter, who lives nearby, rushed to her parents' place, she found the family dead.
Subhash was retired, while his son worked as a lab technician at IIT-Powai. The robbers are absconding and the cost of looted valuables is yet to be ascertained.