 However, they again had no success, and the robbers escaped.That same year, former lawman, scout, tracker and longtime killer for hire Tom Horn began his investigation on the Wilcox robbery case, working on contract with the Pinkerton Detective Agency to solve the case, and with whom he had been employed many years before.He generated productive information which was later passed to Charlie Siringo via the agency, obtained from explosives expert Bill Speck.