Clues found from the dead, a photo, a person's name, how would you infer evidence?

China painter's horse painting is Xu Beihong's ink painting, but the body of the deceased is a pencil sketch. I don't know how to understand drawing marks. Is the drawing mark signed by the author? Is this a death message? The murderer's last name is Ma? Last name is Xu? Tear off the corner in the upper left corner of the work. What do you want to express? The name is Ma Jiao. Jiao Xu? But your question is really confusing. What do you want to know? The conditions are not clear. ..