Zhang had taken a team to visit a remote mountain area where they were tasked to prevent a fight among local residents over the harvesting of a Chinese caterpillar fungus.

They spent 40 days in the area – which had no telecommunications access – starting in May, before returning from a farm on June 14.

On their way back, near the mountain, they were ambushed by gunmen. Zhang was shot dead.

Police investigators have concluded it was a revenge attack and that Xue, whose village is under Xinlong, was involved. Police are offering a 500,000-yuan (HK$620,000) bounty for his capture.

Local government officials have sent their condolences to his family. Zhang graduated from the Aba Normal School in Sichuan in 2002 and worked in a police station.

He worked his way up the ladder, becoming part of the anti-vice squad before being transferred to the politics and law committee in June 2012.

Local police have issued an arrest warrant for Xue and since yesterday have put out wanted posters with his mug shot.

The government’s stability drive ranges from crackdowns on protests against land seizures to internet censorship and muffling the dissent of religious and ethnic minorities.

Simmering ethnic tensions in the region has spurred at least 119 Tibetans to set themselves alight in protests against Chinese rule since 2009, often in heavily Tibetan areas of the provinces of Sichuan, Gansu and Qinghai. Most have died.

With additional reporting from Reuters