Police seek why 72 year old gunman shot up LA dance hall

Investigators searching for a motive in the worst mass shooting in Los Angeles County history say a search of the gunman's home discovered a rifle, hundreds of rounds of ammunition and evidence he was manufacturing gun silencers.

Los Angeles Sheriff Robert Luna said Monday that investigators have not yet established Huu Can Tran's motive in the massacre, which happened during a celebration of Lunar New Year at a Monterey Park dance hall.

The assailant fired 42 rounds at the Star Ballroom Dance Studio, where 11 people were killed and nine wounded.

Luna says a hero later disarmed the gunman, who later was found dead from a self-inflicted gunshot.