The event was usually reported in the local papers, so a search of their archives would find it. The archives would have to be digitized or otherwise well-organized, and one should be able to set a time interval for the search, in order to cut down on time and expense.

Most papers and journals charge for use, so not cheap or easy.
Some of the more common songs (Frankie and Albert sort of song) have books and articles written about the event, so library and internet search usually turns up the information.

I have paid an archive for copies of rare sheet music a couple of times. Expensive!

Often the folk song bears little relation to the story- singers make up what they think is a better one.