Report to your ins co and let it fight it out. If minor, you can sue the other driver in small claims. Without seeing the scene and having all details, it is hard to comment on liability. If you had just pulled up or it was dark, and he was backing, it could be your fault. If you were plainly visible and he just didn't look before backing, it could be his fault.
Your standing in a fire lane is irrelevant as far as whose fault the accident was. Usually, though, a driver who is standing still is not at fault when the rear of another car impacts his passenger door.
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