He had a shining reputation, except for the period (1891–1892) when he worked for his brother-in-law, the infamous badman, Soapy Smith in Denver and Creede, Colorado.
[1] In the fall of 1889, Sam Hasley, a trouble-maker with a deputy sheriff's commission, that allowed him to carry a gun, was drunk causing problems in Belton.
Light ordered him to go home; instead, Hasley rode his horse onto the sidewalk, daring the young lawman to do something about it.
In 1891, William Light joined up with his brother-in-law, Jefferson Randolph Soapy Smith and his criminal empire in Denver, Colorado.
Soapy urged his brother-in-law, William Light, to accept a position as camp deputy marshal.
William "Reddy" McCann, a Creede faro dealer, with a killing history of his own, was drinking heavily one night.
William Light returned to Temple, Texas, where in June 1892, he applied for a position as a detective for the Gulf, Colorado & Santa Fe Railroad.
At the hearing, Coggins rose from his seat and pointed his .44 revolver at Light's head and fired several shots.
On December 24, 1893, while heading home Christmas Eve on a Missouri, Kansas & Texas train car, William Sidney "Cap" Light, accidentally pulled the trigger of the revolver in his pocket.