There are a couple of other helps you can use to help with the meaning:
Long and other Bureau of Prisons officials say...
I take it that you realize the part in italics is a noun phrase that goes with the verb 'say'.
First, its a plural verb, so the subject will be plural.
Second there is the word and, which we might expect joins together the two subjects of 'say'.
If you have realized that Bureau of Prisons acts like an adjective of officials, you can remove the adjective, since they are optional.
You now have Long and other officials. The 'other' hints that Long must somehow be an 'other' official.
How can that be? That is not easy for you, if you are thinking about the English word long.
Perhaps it would have been easier to recognize that Long was a proper noun if it was not the first word of the sentence. Both proper nouns and the first word of a sentence are capitalized. So, if a proper noun is the first word, the fact that it is a proper noun gets camouflaged or hidden.
So, yeah, look around for a possible meaning of another official that could be a proper noun, Long. And as Jay points out, there is a Mary Long in the previous sentence. So you can infer that the Long in 'Mary Long' provides the 'other official' you are looking for. Plus, it helps that this Mary Long is described as an 'officer', which can be a synonym for 'official'. Of course it helps immensely to know that Long is a surname. But many common, common nouns are also surnames. Ah, you learn by experience, just like native speakers do.