John D. King 1850-1910 1st TN Infantry buried in Alabama

A friend of mine is trying to solve a mystery. She is researching Confederate burials at Forrest Cemetery, located in Gadsden, Etowah County, AL. There is a confederate marker for John D. King 1850-1910, Co. I, 1st TN Infantry. There is also a Confederate marker at King Cemetery in Athens, Limestone County with the same info. She has found John D. King in Limestone County on the census. She has NOT been able to find a John D. King on a census in Etowah County. She is an fairly experienced researcher but this one has her pulling her hair out. Why are there two markers with the same info? Are there two John D Kings or was the one from Lawrence Co. visiting here and died? she tried to call the cemetery office today to check to see if they have additional info on the people that are buried in this plot. Also in this plot are Harris King 1930, Wm King 1923, and Fannie A. King 1918-1921, Lila Baker King 1889-1964, Robert King(attorney). She is having no luck finding a death certificate on this soldier? Any help or suggestion would be appreciated.