Transcript for Diary entries shed light on murdered American missionary's final hours

This is what god has called him to do, which is to go and share the love of god with these people. Reporter: Contact with the sentinelese people is illegal because it could expose them to our diseases which could prove deadly. Unable to communicate with outsiders, the tribe is known to be hostile. After the 2004 tsunami, this tribe member was seen firing arrows at a helicopter sent to check on their well-being. CHAU seeming to acknowledge those potential dangers his actions could bring, writing, quote, I think I could be more useful alive, but to you, god, I give you all the glory to whatever happens. Forgive any of the people on this island who try to kill me, especially if they succeed. Now local Indian officials believe they know where the American missionary is buried, but it may not be possible to retrieve his remains without endangering more lives. As for the fishermen who helped him get to the island, they have been charged with culpable homicide. Do we have any idea the number of isolated tribes like this that are out there? There are about 100 uncontacted tribes around the world, and this is serious because it could expose them to disease. They don't have the immune systems we do. Thank you, Paula.

This transcript has been automatically generated and may not be 100% accurate.