What happens at the end of "The Story of an Hour"?

In "The Story of an Hour," Mrs. Mallard receives news that her husband has died in a tragic "railroad disaster." She immediately accepts the knowledge and weeps immediately "with sudden, wild abandonment." And then a shift occurs.
Mrs. Mallard retreats to her room in solitude to process the significance of the news. She reflects that "she had loved him—sometimes. Often she had not." And she sees this change in her situation as a move toward freedom.
Indeed, she repeats this phrase to herself several times: "Free, free, free!"
Finally, she has a chance to live for herself. She will be able to make her own decisions and not be forced to submit to her husband's whims and desires.
Then, a surprising twist occurs. She emerges from her bedroom, and her husband suddenly appears at the door, "a little travel-stained, composedly carrying his grip-sack and umbrella. He had been far from the scene of the accident, and did not even know that there had been one."
Mrs. Mallard's heart, already looking toward her new future with great excitement and anticipation, cannot take this shift back to her old life. The shock and disappointment that her husband is very much alive stops her heart and kills her.

At the end of "The Story of an Hour," Louise suddenly realizes that what she thought was her new-found freedom was just a mirage. Upon hearing of the news of her husband's death, Louise was ecstatic; for the first time in her adult life she felt as free as a bird. All of a sudden, new vistas of opportunity appeared before her eyes, giving her a glimpse into a bright future of personal freedom and self-fulfillment.
But all that is cruelly snatched away from Louise when she discovers that her husband didn't die after all and that she is destined to remain trapped in a stultifying, loveless marriage for the foreseeable future. Her weak heart cannot handle the stress of seeing her husband walk through the door and so she drops down dead on the spot.

Throughout "The Story of an Hour," Louise Mallard believes that her husband Brently has been killed that day in a railroad accident. In the hour after receiving this information, Louise cries and thinks about her husband, believing him to be a kindly but, at the same time, oppressive force in her life.
Louise reflects on the hold that people in relationships have on each other, and it occurs to her that it seems a "crime" when men or women "believe they have a right to impose a private will upon a fellow-creature." Louise begins to process the fact that Brently's death means that she will be able to think and make decisions for herself, and she allows herself to feel some joy at her impending freedom.
What happens at the end of the story is that Louise's husband Brently walks in the front door; he had not been the victim of a railroad accident. Though her husband's friend Richards tries to screen Brently from Louise's view, she sees him, and she literally drops dead. The doctors who come attribute her death to "joy that kills," meaning that they believe that she is overjoyed to see Brently return and her heart gives out. However, the feminist reading that Kate Chopin may have intended suggests that Louise dies of a broken heart because her freedom is abruptly snatched away before she can begin living her own life.