It’s an excuse for Chinese authorities to crack down on the Uyghur population much like they have the Tibetans.
I have found two articles that indicate that the PRC planted disguised policemen and/or soldiers in the crowds of protesters in Lhasa to initiate rioting. The aim was to be able to point to the Dalai Lama and accuse him of inciting violence. Here is the one I think I can post on FR without copyright problems.
Chinese Regime Implicated in Staging Violence in LhasaUPDATED