Very true, with the possible exception of certain contract murders of the very wealthy, famous and or well known mobsters, that were killed by professional killers.
My hunch in this case is Mr. Smith was involved, as someone who loaned the gun to a former prison associate, or was given the gun by an acquaintance after the victim was murdered...
Something led the investigators to Smith...That information seems to have been very credible, indicating they're on the right track.
I read someplace - can't remember where - that a tip actually came into America's Most Wanted. I have not seen it reported anywhere else, so it might be BS.
And I agree with your comments about the wealthy and the mob (excluding government-sanctioned hits, of course).