fallen tree borderline the sidewalk

Hi folks,
I live in Los angeles and a big branch of an old tree that borderlines the sidewalk on my yard has fallen, fortunately nothing is damage and no one is hurt. I called city hall and they told me they don't want to take responsibility of cleaning it up and taking care of the tree. The worker told me that he doesn't know who planted the tree and he just said it's not a city tree. I saw from time to time that city workers wearing uniform were trimming the tree and he told me even if it's true it was a mistake. I don't trust anything he says. Can someone advise me how to proceed?
thank you!!

Till you find out who actually owns the tree, no one can answer your question.

Well the problem is that no one knows who own the tree. The city worker told me that the tree was there long before he arrived 20 some years ago and he just assumes that it belongs to some previous owner of the house. But he doesn't have a clue.

If the tree is dying and falling apart then your might have a claim with the owner of the land - If mother nature caused the limb to fall, and the tree is mostly healthy - you have no claim.