He joined the Survey of India in the 1960s, set off to map the uncharted Andaman and Nicobar Islands and came upon North Sentinel Island. Landing there not once but three times to do his job, Major General HK Sinha was then a young captain but knew when to stop trying to make contact with the aboriginal Sentinelese tribe that lives on that island and allegedly killed a young American who landed there to try and get to them the word of Christ.