According to a local police spokesman, the incident occurred in the city of Thane, some 32 km north of Mumbai, early Sunday after Hasnin Anwar Warekar, 35, took the lives of his family members in bed with a butcher's knife.
"The attacker, Hasnin Anwar Warekar, hung himself after slitting the throats of all other family members including his parents," said police spokesman Gajanan Kabdule.
Warekar's extended family - three sisters, their children and his parents - were among those who apparently had gotten together for dinner, Kabdule said. Warekar's wife and two young daughters were also in the house and were among the dead.
One of the sisters of the assailant reportedly survived the attack, and is being treated for her injuries in hospital.
"We came running. His sister was shouting from the window for help. We saved her by breaking the window. When we tried to break through the door she asked us not to as her brother was holding a knife. My elder brother and I went to call the police," said a neighbor.
Kabdule noted, "We still haven't been able to speak with the attacker's 21-year-old sister, the lone survivor of the attack, who is in deep trauma at a city hospital."
The police spokesman said investigations are underway to find the motive behind the deadly attack.