Can my landlord toss my storage items without my permission? I'm still a tenant?

I'm living in an apartment and have used a storage unit in the back of our building for six years. Every tenant gets one. They are not #'d, nor igned, and from what I recall, the lease does not speak of these storage units, but, again, everyone in the building has one. A new tenant moved in, took my storage unit, and tossed my things away without asking. Mostly, they were personal items, some were rare books. Is this legal? What am I entitled to in terms of a monetary claim if I can't produce a receipt? The items were dozens of years old