The author of this post is a volunteer editor for news site inmediahk.net, which is quoted in this report.
An attempt by student protesters to occupy roads around the Hong Kong government's headquarters led to a series of violent clashes with police on November 30.
As pro-democracy protests in three major finance and commercial districts in the city enter their third month, the Hong Kong government continues to ignore protesters’ demands of free and fair elections. Instead, it recently worked behind the scenes with pro-Beijing groups to press the court to issue an injunction order to legitimize police efforts to clear the protest sites.
In response to the clearing of the Mong Kok site last week, two student activist groups, the Hong Kong Federation of Students and Scholarism called on protesters to occupy major roads outside the government's headquarters, an area which is not covered by the court injunction.
A series of violent clashes took place late at night when protesters attempted to break through the police line. The protesters managed to occupy Lung Wo road for a few hours, but police beat back the crowds with pepper spray, tear gas and batons the next morning.
The student activist groups admitted  their failure and apologized to their supporters, saying they did not anticipate the police's “out-of-control” aggression. On the other hand, the government described the protesters as “rioters” who deviated from the principle of “non-violent protests”.
Meanwhile, a large number of witness accounts have appeared on social media. Jon Ho, who says he was beaten up by the police, described  how the police acted and showed off his bruise on citizen media platform inmediahk.net:
At 2 a.m. on December 1, I was standing in the third or fourth row among the front lines of protesters on Lung Wo road. I equipped myself with goggles and a helmet. Suddenly, I heard people scream and without much thought, I pushed forward.
I thought I should be safe as there were so many in front of me. But they were quickly pulled away by police and I was then in the second row, facing the special task force police. Then I was pushed and fell down.
My eyes and face were covered with pepper spray. The goggles were broken. I fell on the side of the protesters and someone stepped on me. My mind went blank […] I was dragged by a police officer and a few others started kicking me. I thought, oh hell, they would arrest me. I lay motionless and pretended to be unconscious. The police then turned their attention to others.
While I still pretended to be unconscious, something horrible happened. A police officer attacked my motionless body with baton. This was pure violence out of rage. In any circumstance, attacking a defenseless person who is lying on the ground is absolutely wrong. I was very angry. Then another cop came and stopped him, “Hey stop beating him.” I was fortunate to avoid further torture.
Hong Li Fong, a writer at inmediahk.net, believed that the “out-of-control” violence of police is a result of the “Lucifer Effect “:
I saw that the police officers were very satisfied with themselves after clearing the protesters, as if they had done something great. I saw that they did not hesitate to hit people with batons and pepper-spray protesters, as if the protesters had committed very serious and unforgivable crimes. I believe there are still some good cops. But I have never encountered any cops who show regret on their face. Some say it is the Lucifer Effect, I believe so as well. [In the eyes of the police], we represent evil and they represent justice, we are rioters, even though we are just having peaceful sit-in.
Gordon Mathews, an anthropology professor from the Chinese University of Hong Kong, also protested with his students on that night. On Facebook, he criticized the political elites for their failure to address young people's aspiration: 
The news tonight is full of claims by police and Hong Kong government figures that protestors had become violent. Perhaps a few somewhere were—but overwhelmingly the violence was committed by police beating students with their batons with great force. Now, the protesters were indeed engaged in illegal behavior—they were occupying roads around the Central Government Complex, in an expansion of their earlier protest zones. Some force was probably needed to clear the roads. But many police were behaving in an out-of-control way, as dozens of videos on TV and YouTube attest. This does not compare to police brutality in the United States: we have had no shootings, and, I pray, this will continue. Hong Kong is still more civil in its behavior than almost anywhere else in the world. But the police have become politicized, largely because of Hong’s political leaders hiding from sight, and a generation of Hong Kong youth has emerged that see the police as their enemy.
The Occupy Central movement will end very soon, although many more demonstrations will take place in the coming months and years. The long-term legacy of the movement will be a vast generational chasm. On Hong Kong university campuses, the overwhelming majority of students support Occupy Central and its civil disobedience, think that the Hong Kong government is run by incompetents who have no understanding of how ordinary people live, and see the mainland as a foreign dictatorship rather than a motherland. This is totally different from what Hong Kong and Beijing pundits envisioned twenty years ago, and was not even fully imaginable twenty months ago. A generation has been radicalized. Will this generation be running a new, more democratic and open Hong Kong in the future? Or will it suffer a sterile, plutocratic, authoritarian Hong Kong? I feel so proud of Hong Kong students, and so full of a bit of hope and a lot of fear about the future of my city.