Visits to India's Andaman and Nicobar Islands are heavily restricted as the people resists outsiders, often attacking anyone who comes near.
Despite this, John Allen Chau from Alabama decided to go there, with the help of seven fishermen who helped him get there and whom have now been arrested for doing so.
He described himself in his twitter bio as: "Adventurer. Explorer. Wild. Kingdom Seeker." and had been a student with Oral Roberts University missions in the past, an evangelistic organisation.
William Wilson, President of ORU missions, said: "We are not surprised that John would reach out to these isolated people to share God's love".
Police said Mr Chau arrived in the region on 16th October and stayed in a hotel while he prepared to visit the prohibited island.
He was apparently killed by arrows, but the cause of death cannot be confirmed until his body is recovered.
Police have approached anthropologists with contacts on the island in an effort to visit and recover the body.
He interacted with some of the tribes people, giving them gifts he had prepared such as a football and fish. But the tribes people became angry and shot an arrow at him which apparently hit a book he was carrying
CNN report that one of his friends, John Middleton Ramsey, said: "I see him as a martyr,
"He was someone who died out of love for these people to bring the good news of Jesus Christ."
After his kayak became damaged on 15th November, he swam to the fishermen's boat, which was waiting at a prearranged location and spent the night there, writing out his experiences on pages of paper which he gave to the fishermen, police said.
According to South China Morning Post, a source who saw the notes said John Chau wrote that he was: "doing this to establish the kingdom of Jesus on the island ... Do not blame the natives if I am killed."
In an interview with The Outbound website 4 years ago, he listen among his inspirations: "Adventurers like John Muir, Bruce Olson, and David Livingston inspire me to go travel and explore, and I definitely get my inspiration for life from Jesus."
David Livingstone was a missionary in the 19th century and Bruce Olson is an American Christian who has spent his life spreading the gospel.
He set out again to meet the tribes people on 16th November.
But the following morning, the waiting fishermen saw from a distance his body being dragged by tribesmen.
They left for Port Blair, the capital of the Andaman and Nicobar Islands, where they informed Mr Chau's friend, who notified his family.
His family got in touch with Indian police and US consular officials.
Police arrested the seven fishermen and charged them with endangering the life of the American by taking him to a prohibited area.
However, director general of police in Andaman and Nicobar, Dependra Pathak, told TNM: "He lived in Alabama, US. He is some kind of paramedic. He was on a misplaced adventure in prohibited area to meet uncontacted persons.
"People thought he is a missionary because he had mentioned his position on god and that he was a believer on social media or somewhere online. But in a strict sense, he was not a missionary. He was an adventurer. His intention was to meet the aborigines."
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