Can i enter a storage unit belonging to my late boyfriend if I have the code and key but I'm not on the lease?

My boyfriend passed away last month. He has a storage unit with personal memoirs that may help me reach closure on this. I'm not on the lease but have his code and key. One storage manager told me that I can just walk in and get what I need. As long as I have the code and key. It's if I don't that they can't give me info. I'd have to go to court to get an affidavit with a death certificate. Can I legally enter without going to court if I have the code and key? What happens if I do and was given the wrong answer?