The Mass Murder at Santa Monica College

From June 9, 2013 CNN:

Police had contact with the gunman in 2006, but because he was a juvenile then, authorities couldn't release further information, Santa Monica Police Chief Jacqueline Seabrooks said.

A law enforcement source with knowledge of the investigation told CNN on Saturday that the gunman had suffered mental health issues. A few years ago, he was hospitalized for treatment after allegedly talking about harming someone, according to the official.

It's not clear whether the state government or his family committed him for treatment or whether he committed himself. It's also unclear under what circumstances he was released.

And yet California has had an assault weapon ban since 1989  (the year the shooter was born) and on transfers of high-capacity magazines since 2000 (when the shooter was eleven years old).  It has required all firearms transfers to be done through a background check since 1991 (when the shooter was two) and it appears that the shooter had been committed at some point -- which is one of the things the California background check includes.