The teenager, identified as Chris Singh, underwent surgery at a Fresno hospital for head trauma after he was shot by his father on Saturday, local newspaper Fresnobee reported.
Doctors have said his injuries were life-threatening, without giving further details.
Spokeswoman of the Community Regional Medical Center, Mary Lisa Russell said that the boy was in critical condition.
Fresno County Sheriff Margaret Mims said Avtar Singh, a former Indian army major who owned a Selma trucking company, apparently shot and killed his wife and two other sons, ages 15 and 5, before killing himself. Mims said Singh called Selma police at 6:15 a.M. On Saturday to report that he had killed his family and was going to kill himself.
While two children and their mother were found dead along with Singh, the eldest child was in a gravely injured state.
Authorities have not yet officially released the names of Singh's wife or the two sons who were killed.
According to Fresnobee, Singh was arrested in February last year after his wife accused him of trying to choke her. That is when police discovered that Singh was wanted in India on a murder charge in the 1996 death of human-rights activist Jaleel Andrabi in Jammu and Kashmir.
The people in the community where Singh and his family lived were shocked with the incidents.
"Our community is completely shocked...It's a misfortune, especially for the children who died," said Rajbir Singh Pannu, president of the town's Sikh temple. (MORE)