[Here’s a timeline of how Hong Kong’s protests have progressed and evolved.]

The hard-line protesters see themselves as being forced to mete out justice in a system that lacks accountability and in the face of a government they deem unresponsive. Much of the violence has been fueled by anger over police conduct, made worse after an officer shot a teenage protester in the chest with a live round during clashes on Oct. 1, the politically sensitive anniversary of the founding of the People’s Republic of China.

But to their critics, these protesters are crossing the line by playing the role of vigilantes to punish those they consider their foes. The intensity of the unrest could alienate moderate supporters and members of the public, and play to Beijing’s depictions of the movement as the work of riotous mobs.

“Some people began to take matters into their own hands,” said Ma Ngok, an associate professor of government at the Chinese University of Hong Kong. He pointed in part to the protesters’ frustration that the police have in large part failed to arrest and prosecute pro-government thugs who attacked demonstrators.

Yet, he added, in recent days, the movement has been debating whether such retributive violence is morally justifiable.