I Wasn't on the Lease, Am I Liable

My question involves a roommate in the State of: CALI

Two bedroom apartment. I shared a room with one guy "B" and the other guy had one room to himself "A." A is the only tenant on the lease agreement, but B lived in the apartment far longer than I did. I was there for less than four months and paid a little over half of B's share of rent. We were in the process of deciding whether I wanted to stay there after B had left (vacation in Europe) or move out at the same time. My agreement was with B not with A.

If anything A&B should be having this discussion with each other. Anyways, the unit was broken into and items were stolen. The complex was a shady place to begin with and I never intended to stay there long-term and had never stopped looking for another apartment and B was aware of this. I told B that I would be moving out and they both agreed. The landlord had asked if we would be out before the 1st of the next month, I had already vacated the premises before then and the only person who didn't move any of their belongings out was A. Since he didn't do that, he would still have to pay rent.

He has been pursuing ME for that share, my question is am I responsible for paying him?

He being the landlord, or your roommate? "That share" being a share of what?

I mean my roommate, and the rent that he was responsible for paying for April as he did not move his belongings out in time. But he was the only one on the lease, does that make him MY landlord?

Was I legally bound to give my roommate 30 days notice, considering the special circumstance?

*Update: I found out he may have filed a claim against me in small claims court.