Shocking scenes of pro-democracy protesters at Hong Kong's airport beating two men accused of being infiltrators have sparked soul-searching within the movement over whether a minority of radicals are undermining their cause.
Debate has appeared on web forums used by protesters -- and one group even issued an apology -- after Tuesday night's chaotic scenes in which paranoia about undercover police reached new heights.
In separate instances during a paralysing occupation of the city's airport two men found themselves at the mercy of a mob.
One was accused of being a mainland police officer and another of being a spy masquerading as a journalist.
Both were detained, had their limbs bound by zip-ties and were beaten until crowds of fellow demonstrators and firemen managed to usher them to waiting ambulances.
Beijing, which has refused to offer any concessions to protesters, jumped on the assaults Wednesday, accusing protesters of adopting "terrorist-like actions".
Within the protest movement there was a palpable uneasiness over how Tuesday's violence had unfolded.
"After months of prolonged resistance, we are frightened, angry and exhausted. Some of us have become easily agitated and over-reacted last night," one group, which has organised anonymous press conferences featuring protesters, said in a statement emailed to journalists.
"For this we feel pained and dispirited and would like to express our most sincere apologies," the statement added.
On the Reddit-like LIHKG forum used to coordinate protests, some voiced dismay over the violence.
"We are not like the corrupt cops," one user wrote. "We should admit it when we're wrong."
- Frenzied anger -
Weeks of rallies, demonstrations and occupations in Hong Kong have seen millions of people take to the streets in the biggest challenge to China's rule of the semi-autonomous city since its 1997 handover from Britain.
The movement was initially sparked by opposition to a planned law that would have allowed extraditions to mainland China.
But it has evolved into a much broader campaign for democratic freedoms, and a bid to stop the growing influence of Beijing's creeping authoritarianism.
With 10-weeks of unprecedented protests and increasingly violent battles with police winning no compromises from Beijing or the city’s leaders, protesters this week took their civil disobedience campaign to the airport, one of the busiest in the world.
Activists argued that increased levels of police violence -- including a protester who reportedly lost an eye to a bean-bag round -- had forced them to up the ante and hit a soft target, even if that meant disrupting travellers.
But ever since police disguised themselves as protesters to make arrests last weekend, fears of interlopers have exploded.
Kwok Ka-ki, a pro-democracy lawmaker, was at the airport late Tuesday after the crowds had zip-tied their second victim to a luggage cart.
It later transpired the man was working for the Chinese state-run and vociferously anti-protest tabloid the Global Times.
Kwok pleaded with the largely young protesters not to beat the man.
"We shouldn't do anything to harm him," he told AFP, recalling the night's events.
"Even if he was actually doing something unlawfully, we should not get into the same position as the government or the police," he added.
- Peaceful rally planned -
Yet some within the protest movement remain unapologetic.
One 19-year-old, who wanted to remain anonymous, admitted to hitting one of the detained men.
"I don't think this is going too far. They are the enemy," he told AFP.
"Everyone's emotions were really high, because there have been too many injustices done to us," added another protester, who gave her name as Sav.
On the LIHKG forum some were adamant the two beaten men were legitimate targets.
The violence poses a challenge to a movement that has successfully pushed a mantra of unity over the last ten weeks.
One chant and slogan that is often daubed on walls roughly translates as: "Even in a nuclear explosion, we won't sever ties."
The Civil Human Right Front -- a non-violent group that organised record-breaking rallies early on -- has vowed to hold a fresh march on Sunday in an attempt to show the movement still retains popular support.
Dixon Sing, a political analyst, said the more moderate elements were already issuing apologies to travellers for the airport disruption.
"Among the protesters, it's very pluralistic," he said.
"There's a more rational wing that pays close attention to the tide of public opinion and they take action to rectify the more radical and emotional acts as soon as they can."