'Vicious circle'

An is a member of the Yi people, an ethnic group in the mountains of Southwest China. When he was young, many Yi were mired in poverty. As they faced obstacles accessing education, illegal narcotics became prevalent among them.

"Once people become addicted to drugs and find themselves unable to pay for their fix, they are likely to get involved in the business. That creates a vicious circle from which almost no addict can escape," An said.

His understanding of the nature of the crime makes An more determined to end the trade. He does not see himself as a savior, but as a man of the law who believes that officers such as himself form a bottom line that can prevent young people like Liu passing the point of no return.

"The intelligence we received during border scouting missions showed that Liu was only in his 20s. People his age are usually students, ready to open a new chapter of their life, rather than criminal suspects targeted by police," An said.