30-year-old son were today found murdered at their residence in Chhaya area of Porbandar city, police said.
The deceased were identified as Parbatram Vadhiya (65), his wife Lakshmiben (62) and their son Jayanti (30).
Police suspect that the mentally-challenged elder son of the deceased couple could be behind the crime.
"As per the wounds found on the victims' bodies, it is clear that they were hacked to death with an axe," Deputy Superintendent of Police Porbandar town M D Jadeja said.
The victims were found lying in a pool of blood at their residence by some of their neighbours, he said.
Police have launched a search to nab him.
A case has been registered at Kamlabaugh police station in the city in this regard.