This sort of things was far less common than we might think given how ubiquitous the motif is in Westerns - films and television shows about the "Wild West." That said, there would need to be some proof of the outlaw having been killed, if he couldn't be brought back alive (which would always be the more convenient option!).

The case of Joaquin Murrieta (also Murieta or Murietta) (1829-1853) provides an example of one of the possibilities. Murrieta was an outlaw who became legendary even before his death in 1853. He quickly became a fixture of local folklore. Even after his death, Murrieta was such a potent force in local oral tradition that many believed he had not died but rather was continuing his escapades.

Murrieta was sensationalized by a dime novel, by John Rollin Ridge (1854). His unverified story included an attack of his group of law-abiding Mexican miners by Americans. Injustices included the rape and murder of Murrieta's wife, the whipping of Murrieta, and the lynching of Murrieta's brother or step brother. The following crime spree, to answer these alleged wrongs, resulted in the formation of a formidable gang, known as "the five Joaquins" (because all five robbers were named "Joaquin"). Folklore claimed that the gang was stealing gold from Americans and giving it to poor Mexicans. Governor John Bigler created the "California State Rangers" to pursue Murrieta and his gang. On July 25, 1853, the rangers killed three and captured two others, who they believed were the "five Joaquins." The rangers chopped off the head of the one they believed was Joaquin Murrieta and brought it back in a jar of alcohol to the authorities for the reward. Along the way, the rangers charged people one dollar to see the head. The story of Joaquin Murrieta may have played a part in inspiring the story of Zorro, first appearing in 1919.

Source: Frank F. Latta, Joaquin Murrieta and his Horse Gangs (Santa Cruz, California: Bear State Books, 1980).