This is based on a folk song about a man named Railroad Bill. According to the Encyclopedia of Alabama, Railroad Bill was an armed African-American vagrant who was reported to be riding trains starting around 1895. After some violent encounters with law enforcement officers, Railroad Bill was the target of an increasingly intense manhunt until he was killed in 1896. In the meantime he became something of a folk hero, with stories of him being able to shapeshift into animal form and only being vulnerable to silver bullets, and so on.
This is based on a folk song about a man named Railroad Bill. According to the Encyclopedia of Alabama, Railroad Bill was an armed African-American vagrant who was reported to be riding trains starting around 1895. After some violent encounters with law enforcement officers, Railroad Bill was the target of an increasingly intense manhunt until he was killed in 1896. In the meantime he became something of a folk hero, with stories of him being able to shapeshift into animal form and only being vulnerable to silver bullets, and so on.
Source: http://www.encyclopediaofalabama.org/face/Article.jsp?id=h-1258