An unemployed man shot and killed his wife, three children and mother-in-law before taking his own life over his family's financial difficulties, police said.

Los Angeles Police Department deputy chief Michael Moore said the gunman, 45, shot his wife, 39, her mother, 70, and three sons aged 19, 12 and seven at their home in an upmarket suburb of Los Angeles.

The identities of the family members were not released, but Moore said the gunman was a business school graduate who had held jobs with accountancy firm Price Waterhouse and Sony Pictures before becoming unemployed.

"We believe this individual had become despondent recently over his financial dealings and the financial situation of his household and this murder-suicide event is a direct result of that," Moore said yesterday.

A letter apparently left by the gunman attested to the family's financial difficulties, he said.

California is one of the worst-hit states in the US home foreclosure crisis, but police said the gunman was not the owner of the home, located in a gated community of Porter Ranch in the San Fernando Valley.

Moore said all of the victims had been shot with a handgun recently bought by the jobless man, who had no history of mental illness or of seeking treatment for mental health problems