Hector Celaya, 31, died on Sunday, several hours after he was wounded during gunfire with Tulare County sheriff's deputies as he tried to flee in a vehicle.
His death was confirmed by sheriff's Sgt. Chris Douglass, who did not release details.
Authorities apprehended him early on Sunday, about six hours after deputies were called to a trailer on the Tule Indian Reservation on Saturday night.
Inside, they found the bodies of a man and a woman; the body of another man was nearby.
Deputies also discovered a wounded young boy, whose condition and age were not known.
Officials said Celaya shot his two daughters, ages 5 and 8, who were found with him in the vehicle when he was apprehended. One girl suffered life-threatening injuries, while the other girl was less seriously hurt.
A motive for the attacks was not immediately known.
The boy who was wounded is believed to be about 7, said Shelby Charley Jr., an engineer and supervisor with the Tule River Reservation Fire Department.
"This is a once in a lifetime kind of deal," Charley said of the call. "It's one of those calls you could go your whole career and not walk into. This is one of those calls that will stick with you for the rest of your life."
The winding roads out of the reservation delayed medical help for the boy, Charley said. Thick fog in the area
prevented a medical helicopter from responding, he said.
At the scene of the shooting, police tape stretched out across the driveway to three modular homes built on a hillside that appeared to be a family compound. The homes are in a remote area scattered with oak trees and rock outcroppings.