The tone could be described as one of complicity and guilt. Note how often Faulkener intrudes with the prounouns "our" and "we," throughout the story, even in the first sentence: "our whole town went to the funeral."
Guilt and complicity can be seen in the way Emily is treated while alive. Once part of a proud (and wealthy) Southern family, she is considered "a duty; and a care; sort of hereditary obligation."
Mistreatment, in the form of negligence, eventually compounds their guilt after Emily's death. The pieces come together. She was lonely, needed help, not judgment and isolation. At the close of the story, Faulkner once again uses "we" to evoke the townsfolks' universal guilt. "We saw a long strand of iron-gray hair."