Who killed Abraham Lincoln's dog Fido?

The classic story of Fido's killing was reported by Illinois State Journal editor J. Emil Smith in 1931. "The circumstances were as follows: Charlie Plank, a half-drunken man, was one day whittling a pine stick when Fido came bounding along and, as usual, sprang forward with his fore feet raised. In drunken rage, the man thrust his knife into the animal, and poor Fido ran away, not to be found for a month after, when his lifeless body was discovered under an old church." Smith misspelled the last name of Fido's killer ... the knife-wielding man was one Charles E. Planck, then 24, a clerk and the son of Springfield grocer Jacob C. Planck.