This link is a Google search for images of Jack Ruby. Scroll through the list and notice that there are none of him wearing a Fedora hat- except when he was shooting Oswald.
But, how does that mesh with Ruby's story? He claimed that he was out sending a Western Union moneygram to one of his stripclub girls, having no intention of killing Oswald or even attending the jail transfer. But then, he took a wrong turn and wound up there. But, he had no recollection of anything.
But, in that case, what was he wearing a hat for, and why was he wearing it so low on his head?