The unidentified father of five left the house and rushed back to help other family members, according to Hemet city police. The 41-year-old father died along with two daughters, ages 4 to 12.
An 8 year old son is in serious condition. A baby, an 11-year-old girl and the children's mother survived the fire before dawn, according to Hemet Police Lieutenant Nate Miller.
Several attempts to rescue the family of seven have been made, according to Hemet fire chief Scott Brown. Firefighters were harmed by heavy fire and airlines that prevented them from extending the stairs, Brown told a news conference.
"Our hearts bleed for the family," Brown said.
The main focus of firefighters now is research, which will analyze all possible causes, including a Christmas tree.
Authorities believe the fire broke out in the family's apartment and there is no suspicion of a criminal case, Miller said.
According to Lieutenant Jeff Davis of the Hemet Fire Department, 45 residents were displaced from the 25-story, two-story building. Davis said the Red Cross is helping provide shelter for some residents while others were able to make arrangements for a place to stay.
Hemet is about 70 miles east of Los Angeles.