This may prove to be an Islamic terrorist incident, but it should be noted that the situation in China is pretty complex. First, there are 1200 or 1300 miles between Beijing and the border of Xinjiang Province. Second, China is very restrictive about Muslim minorities traveling around China or traveling to other countries (they are not even allowed to have their passports in their own possession). Third, in the province just east of Xinjiang Province, Qinghai Province, the local Muslims coexist peacefully with Han Chinese and other ethnic minorities (e.g. Tibetans). Muslims attend and work at Qinghai University in the provincial capital, Xining.
My daughter attends Qinghai University and is the source of my information.