Muslims in China who want to break away from China and form their own Islamic state attacked a group of 70 policemen as they jogged in the street:

The two men who killed 16 policemen in the Kashgar massacre were today identified as members of an ethic group engaged in a shadowy insurgency in China’s north-western Xinjiang region.
The attackers, aged 28 and 33, were overcome and arrested at the scene and have been confirmed as Uighurs, a predominantly Muslim Turkic people, who make up the majority of Xinjiang’s 20 million population.

Although the official media did not spell it out there appears to be little doubt that they were members of the insurgency seeking to break Xinjiang away from China and establish an independent Islamic state of “East Turkistan”.