Kleber was born into a family of innkeepers in Riggau and studied at the agricultural school in Lichtenhof. In 1876, he volunteered and served in the army for one year, where he received much praise. He suffered a crisis and was hospitalised in 1877. Two years later he was released, recovered. In 1882, he passed the forest ranger’s exams and began work as a royal forest commander. He married in 1895 and lived with his wife and six children in Pressath.
A new episode and hospitalisation followed in 1906. Kleber’s brother describes him as a conscientious and calm person who sometimes started acting strange, became immersed in thoughts and incoherent in speech. Before going to the hospital the second time, he fasted, refused to drink, walked hunched over and seemed restless. At the hospital in Regensburg he was described as a restless patient who sometimes seemed completely sane. In 1909, Kleber contracted pneumonia and died at the same institution in Regensburg.