Whodunnit?

I think that whoever captured Che killed him. I do not think it was an individual person that killed him, but probably a group of people who found him. I think that he was probably put to death quickly opposed to tortured. I think by this point, Che was already dead inside. After his physical appearance and transformation, he was no longer Che Guevara, but a radical that was so consumed with his work that he lost track of his own identity.