It was originally reported that Rockefeller either drowned or was attacked by an animal, such as a shark or
saltwater crocodile. The boat was an estimated from the shore when Rockefeller made the attempt to swim to safety, supporting the theory that he died from exposure, exhaustion, or drowning. However, because
headhunting and
cannibalism were still present in some areas of Asmat in 1961, and still are, there has also been widespread speculation based around local testimony that Rockefeller was killed and eaten by tribespeople from the Asmat village of
Otsjanep. Two Dutch missionaries, who were fluent in local languages and who had been living in the area for years, accumulated a large amount of testimony from witnesses. Neither cannibalism nor headhunting in Asmat were indiscriminate, but rather were part of an eye-for-an-eye
revenge cycle, so it is possible that Rockefeller found himself the victim of such a cycle. Under the Asmat belief system, several of the killers, named Fin, Ajim, Pep, Jane, Samut, would have had "sacred obligation to avenge the deaths of the men killed by Lepré". In 2012, Michael's surviving twin sister Mary published a memoir, titled
Beginning with the End: A Memoir of Twin Loss and Healing, about coping with her grief after the death of her brother. The book was issued in paperback in 2014 as
When Grief Calls Forth the Healing. In 2014, Mary Rockefeller Morgan wrote of her twin brother's disappearance:
2014 book on his disappearance In 2014,
Carl Hoffman published the book ''Savage Harvest: A Tale of Cannibals, Colonialism, and Michael Rockefeller's Tragic Quest for Primitive Art'', in which he discusses researching Rockefeller's disappearance and presumed death. During multiple visits to the villages in the area, Hoffman heard several stories about men from Otsjanep killing Rockefeller after he had swum to shore. The stories, which were similar to testimonials collected in the 1960s, center around a handful of men arguing and eventually deciding to kill Rockefeller in revenge for the 1958 incident. When translated, the man was quoted as saying: Don't you tell this story to any other man or any other village, because this story is only for us. Don't speak. Don't speak and tell the story. I hope you remember it and you must keep this for us. I hope. I hope. This is for you and you only. Don't talk to anyone, forever; to other people or another village. If people question you, don't answer. Don't talk to them, because this story is only for you. If you tell it to them, you'll die. I am afraid you will die. You'll be dead; your people will be dead, if you tell this story. You keep this story in your house; to yourself, I hope, forever. Forever. ==Asmat artifacts and photographs==