His father was South Moluccan, and his mother was Indo Eurasian. He studied law at the University of Leiden. In April 1950 he declared the self-proclaimed Republik Maluku Selatan and served as President. After the successful central government attack on rebel capital Ambon, Soumokil fled to nearby Ceram Island where he led small guerilla resistance until he was captured in 1963. He was imprisoned on Java Island and later executed by order of President Suharto in 1966.