He has been beaten, threatened and imprisoned. But the former child soldier and winner of this year's Goldman Environmental Prize says he will not stop until those wanting to destroy the Democratic Republic of Congo's protected wildlife "are held responsible for their actions." "Even if I or others are not able to (make this happen)," says Rodrigue Mugaruka Katembo, "then the future generations will have this information and will do it." Katembo ... has been awarded the top environmental prize in recognition of the heroism he showed in preventing oil exploration inside Virunga - Africa's oldest national park. His dangerous undercover investigations exposed bribery and corruption among officials. The park is home to a quarter of the world's last remaining mountain gorillas, there are less than 900 left globally. Covering the size of a small country, Virunga is more than 3,000 square miles packed with volcanoes, lush forests and mountain glaciers that tear through the Democratic Republic of Congo, Uganda and Rwanda. As a park ranger, Katembo has one of the most dangerous jobs in the region. Amidst political instability, armed poachers and rebels - who have been warring in the park for the past 20 years - outnumber park rangers ten to one. Protecting Virunga hasn't been easy. In 2013, Katembo was arrested and held for 17 days [after attempting] to stop construction of an oil communication device within the park. Local chiefs have [also] offered him bribes, "to help them get oil exploration going in the park," he says.