"I will remain in my post to ensure passenger safety," Dong Qinwei, an officer with the Harbin railway public security bureau in Heilongjiang province, pledged at a symposium on Spring Festival transportation on January 14.

However, the 58-year-old died suddenly the same day on his way back to work. First aid rescuers were unable to save him.

Dong worked at the police station at Harbin's A'chengbei railway station. He became a police officer in 1988, and had worked in different positions at both the Harbin railway station's police station and the bureau's criminal investigation detachment.

As Dong pledged, he had spent the last 34 years keeping people safe. According to colleagues, regardless of his job, Dong's enthusiasm for work never diminished.

Zhao Hongyu, one of his colleagues, said that Dong taught younger officers useful skills and shared his experience with them.

He recalled a case they worked together in May 2002. They were patrolling on a train, when Dong stopped and said that a male passenger was behaving unusually.

Zhao questioned the man, who opened a pack of gum with one hand to calm himself, but didn't notice anything unusual. Dong pulled the man's other hand free and found a bag of marijuana.

Dong often told colleagues that "as police officers, we must be vigorous and energetic, so that the public feel safe when they see us, and we can deter criminals".

The late officer had also faced retaliation from some of those he'd arrested after their release. When his wife and daughter asked him if he could find other work, he replied "I love this job. I'm not afraid of little injuries."

During his 34-year career, Dong solved 100 cases of different kinds and arrested 135 suspects. Together with colleagues, he conducted around 3,000 kilometers of patrols on the railways, during which they discovered 117 hidden dangers.