I found the box to be empty Possibility or for real?

-I found the box to be emptyDoes the sentence above mean that the box was empty for real or mean that I guessed that the box was empty, which means you are not really sure about it but implies only a possibility of the box being empty in a few second when you open it.If the given sentence means that the box was empty for real, then, it means the same as the following sentence, right?:I found the box empty
(1) I found the box empty(2) I found the box to be emptyMy question is what do the two sentences above mean? Do they mean the same? If not, how are they different? Possibility or for real?Could you help me clarify it? Thanks.