Landlord Responsibilities in Assault with a Deadly Weapon from Roommate

[Harry Lectora]

My question involves landlord-tenant law in the State of: California
I was assaulted with a deadly weapon in the apartment that I rent by a roommate, whom I did not know prior to moving here. Our landlord basically turned a three bedroom apartment in to 4 rooms and rented the rooms individually. So none of us knew eachother prior to moving here. Apparently this individual who has a criminal record for prior drug and DUI convictions, was drugged or something when in an inexplicable rege stormed out of his room with a three foot metal object and started beating me on my back and shoulder. He spent three nights in jail and was released due to "insuficient evidence" and has now moved back to the aparment where obviously all of us are scared to death knowing we have a mentally disturbed individual sleeping in the apartment. The landlord says it is not his responsability to deal with roommate issues and is assuming a "not my problem" attitude.
We want to know if the landlord has any responsabilities in this issue. Especifically the utilities are still under his name and he comes and goes in/out at will and unannounced.