What makes "Salvation" by Langston Hughes nonfiction?

"Salvation" by Langston Hughes is a short essay and a chapter of his memoir, entitled The Big Sea. By definition, memoir and essay are both nonfiction forms. A memoir is similar to an autobiography in that it has the writer remembering moments from his life and relaying those to the audience. Hughes is most famous for his poetry, but "Salvation," as a personal essay is definitely a nonfiction text.
The essay is told in first person, as Hughes begins by saying, "I was saved by sin when I was going on thirteen. But not really saved. It happened like this." We can tell from the start that he is going to tell an autobiographical story about his salvation, or his lack thereof. From there, Hughes tells about an experience he had at church as a child. His aunt told him that he would see Jesus and be saved. When he saw Jesus, he would go to the altar and be welcomed by the church community as one of their own. In brief, Hughes never sees Jesus, but he thinks the other children who go to the altar, claiming to have seen Him, are lying. He decides he should lie, too, and be done with the charade. He is welcomed and celebrated as the other children are, but when he goes home that night, he cries in bed because he didn't see Jesus, and further, "now I didn't believe there was a Jesus anymore, since he didn't come to help me." 
The essay reads like a short story told in the first person, but is based on Hughes's personal experience. He makes a very intimate confession at the end of the story about his own faith at that time in his life. Therefore, this text is nonfiction.