Apartment manager says he can't do anything about trespassers?

I live in an apartment in LA. As probably everyone knows, LA has a serious problem with homelessness. One day, I go into the parking garage and see a naked homeless man ripping up a comforter. I tell my apartment manager this and he says he can't do anything about it. I asked him if theoretically a homeless person just decides to live in our garage, would he really not do anything? He says he would confront the homeless person with a group of volunteering residents??? I am aware that when it comes to handling transients, at least in LA, the police can't really do much. But I feel like if someone is trespassing, homeless or not, it is the apartments responsibility to do something right? Is there not some law stating as such? Does anyone know?