A handgun that had been bought Sept. 16 was found near the father's body, Moore said. The father left two suicide notes -- one for police and one for friends and relatives -- and a will.
The notes attest to the man's financial difficulties, and he takes responsibility for killing his family members, Moore said.
The family members' names were not immediately released because police wanted to make sure the children's schools had time to make grief counselors available. The children were sons ages 19, 12 and 7.
The man had a master's of business administration in finance, formerly worked for PricewaterhouseCoopers and Sony Pictures, but had been unemployed for several months, Moore said.
Moore did not specify what financial trouble the man had been in. He noted that the family did not own the home.
PricewaterhouseCoopers spokesman Steven Silber had no immediate comment. Sony Pictures Entertainment spokesman Steve Elzer did not immediately return a call seeking comment.
The gated community, called Sorrento Pointe, is among several developments along curving lanes and cul-de-sacs set on the foothills of the Santa Susana Mountains in Porter Ranch, about 23 miles northwest of downtown.
Ryan Ransdell, who lives across the street, said the house had been occupied by the family for about a year.
"They didn't socialize too much," he said. "They kept pretty much to themselves."
Slideshow archive | ABC13 wireless | Help solve crimes