Police found two men, ages 54 (the father) and 27, and two women, ages 48 and 54, all suffering from gunshot wounds around 8:38 p.m. Thursday, KTLA reported.
Los Angeles County Fire Department Supervising Dispatcher Michael Pittman tells the Los Angeles Times that there were a total of four victims in the shooting.
The son was arrested on suspicion of murder and held in lieu of $1-million bail.
According to the US Centers for Disease Control (CDC), firearms are the cause of death for more than 33,000 people in the United States every year, a number that includes accidental discharge, murder and suicides.
Their names have also not been released by authorities - coroner's officials said Friday that they were still trying to identify the victims and notify their relatives.
But the brother, Wilfred Calzadilla, said Ernesto had generally stopped going to the house because of worries about the father, making an exception on New Year's Eve. The man's own son, 33-years-old, was the one to finally wrestle the gun away from him, but he was forced to shoot his father once - killing him in the process.
A GoFundMe page for Calzadilla has been started by his family with hopes of raising $20,000 for his funeral and to start a savings account for his daughter. His life was cut short and now left a little girl orphaned'.