"If you dare to report us, you'll pay for it. Go away!" a poacher roared at him, a long rifle in his hand. Undaunted, the teenager secretly took a picture of the illegal hunters and took it to the forestry bureau the next day.
His courage even caught the attention of famous primatologist and animal rights advocate Jane Goodall, who called him a "very brave young man".
That young man was Fang Minghe, who is now 27. He is the founder of a youth-led environmental watchdog, Green Eyes China, in Zhejiang province, where he grew up in a rural environment.
From a young age, Fang developed a close tie with nature and compassion for animals. He also became passionate about environmental protection. "I was shy and didn't play ball games well with other kids," he recalled. "I was in my own world."
During a visit to Guangzhou, he witnessed wild animals killed brutally in the wildlife trade. He felt the urge to do something. "Charity starts at home," he said. "It's a pity almost 99 per cent of people in China are concerned only with survival and making money. They think only about today. We can't rely on the government, either."
Back home, he staged an exhibition of his photographs showing the shocking treatment of animals in Guangzhou.
In 2000, a dozen like-minded schoolmates and friends joined Fang's pioneering project for a squad of young inspectors dedicated to combating widespread poaching. Green Eyes was born.
"I hope Green Eyes will help more people see a greener world," Fang said.
A decade later, Green Eyes offers environmental education for middle- and high-school students across the country. It also runs a wildlife protection hotline and an animal rehabilitation clinic. The group has rescued more than 5,000 animals, including dolphins, birds and snakes. Volunteers also videotape illegal wildlife trade practices with hidden cameras.
Fang won the prestigious Ford Environmental Award when he was just 17. He was also invited to the Great Hall of the People in Beijing, where he received a 5,000 yuan (HK$5,918) cheque from the country's environmental chief.
Yet soon Fang was facing a dilemma: should he go to university or continue running Green Eyes? Two months before the university entrance exam, he made his choice: he quit school.
That was a surprising decision by Chinese standards. Every year, more than eight million students vie for a limited number of seats at colleges and universities through a competitive entrance exam.
Fang says he has no regrets. "I can always go back to college," he said. "But I could never give up Green Eyes, which was still a very young organisation at that time. My dream is to officially register Green Eyes as an NGO."
He hopes his initiative will raise public awareness of the need for environmental conservation and wildlife protection across the mainland. "I want to see a pair of green eyes in every corner of China one day," he stressed.
Today, the organisation has more than a thousand volunteers in more than 100 colleges, but Fang feels his work is far from over.
The young conservationist wants to export the ideal of Green Eyes to Southeast Asian countries, which serve as feeders for a wide-scale illegal wildlife trade in protected species to China.
"People always say I'm a workaholic. Days and nights aren't much different to me," Fang said. "Even when I try to stop, my mind keeps running."