A Freemason is a member of the secret society that is composed of craftsmen, such as stone masons, gem cutters, blacksmiths, and goldsmiths, and began in Medieval Europe. A few US presidents have been a member of the Freemasons and still exist today.
Unless the person specifically states that he is a member of the Freemasons, it is hard to know for sure. Masonry in any case is not demonic and has nothing whatsoever to do with demons.