BIG BEAR LAKE, Calif. (AP) -- A Los Angeles police official says investigators are keeping all options open in the manhunt for the former LAPD officer suspected of three murders.

Searchers are combing a snowy mountain east of Los Angeles where Christopher Dorner's truck was found Thursday, but Deputy Chief Kirk Albanese says it's not known if he's on foot either on or off the mountain.

Albanese says a package sent by Dorner to CNN's Anderson Cooper is being reviewed by the LAPD, and that another media source may have been similarly contacted.

The LAPD fired Dorner in 2008. Albanese says it's not known why the violence is occurring now.

Dorner is believed to have multiple weapons including an assault rifle. Albanese says bullets from such a weapon can penetrate body armor.