What's that old JFK quote? Those who make peaceful change impossible make violent revolution inevitable?
The state draws its legitimacy from the social contract. When people no longer feel like the social contract is beneficial to them or to society - ie as one might feel with a healthcare system that is 100+ years out of date and has received one (1) bandaid for normal folk in the past 50 years - the state can no longer expect individuals to uphold their end of the social contract (adherence to laws, norms, and peaceable conduct).
This doesn't mean "the overthrow of the government is coming tomorrow", but rather means that the social contract is beginning to fray, and a failure of those in power to recognize and accede to that fact (by making major concessions) will result in this sort of incident continually intensifying until... well, until the social contract is gone to a large swathe of people, and then at that point, the overthrow of the government will be imminent, for better or worse.
All interactions between state and citizen are implicitly negotiated. Negotiations require leverage. Violence has always been a form of leverage. But assassinations are far more powerful leverage than riots.