Last Thursday afternoon Volodymyr Rybak, a city councillor in the east Ukrainian town of Horlivka, took part in a "flash mob" demonstration in support of the unity of Ukraine and then tried to raise his country's flag to replace the separatist Donbass Republic's rising-sun banner flying above city hall.
A scuffle ensued and four men, one wearing military fatigues and a black balaclava, bundled him into a car; his telephone was switched off. On Saturday the body of a man thought to be Mr Rybak showing signs of torture – stab wounds to the stomach, bruises on the chest – turned up in a river near the separatist stronghold of Slavyansk, more than 50 miles away.
After his wife Elena and son Yura travelled there to identify the corpse at the city's morgue on Wednesday, Ukraine's interior ministry confirmed this was indeed the slain politician, whose body was found with that of a second, still unidentified man.
Mr Rybak's death adds to a growing file of vigilante "arrests" and disappearances of politicians, activists and journalists – blamed on armed separatists – as law and order erode, the civic fabric frays, and fear of violence grows in Ukraine's east.
"The fact that people are disappearing in Ukraine – in the centre of Europe – in 2014 is simply horrible," Yurii Zhuk, a pro-European city councillor who saw Mr Rybak half an hour before his death, said on Wednesday, looking out the window of the city hall to the plaza – overlooked by Lenin's statue – where the abduction occurred. "It shouldn't be happening."
Oleksandr Turchynov, Ukraine's acting president, made reference to Mr Rybak's case on Tuesday evening when he accused "terrorists" in the east of torturing and killing "Ukrainian patriots", even as he announced plans to resume Kiev's suspended security crackdown on secessionist forces.
The Donetsk-based website Novosti Donbass and the Kyiv Post newspaper on Wednesday published a list of 11 people kidnapped in Slavyansk and Horlivka over the past week. The list included Mr Rybak and Slavyansk's elected mayor, Nelly Shtepa, who disappeared last Friday after trying to meet the city's self-proclaimed "people's mayor", Vyacheslav Ponomarev.
Journalists who have been detained include the American Simon Ostrovsky, whose work included vivid video reportage of the violent takeover of Horlivka's police station last week, and Ukrainian Serhiy Lefter, who was kidnapped by unknown people on April 16 while reporting in Slavyansk.
"We see armed men who oppose the Kiev government acting completely outside the law in the east," said Yulia Gorbunova, a researcher covering Ukraine for Human Rights Watch. "They have absolutely no legal status to be seizing or 'arresting' people, as they call it."
The rights group is also voicing concerns over the Ukrainian authorities' prosecution of separatists for speaking out in favour of secession, as opposed to engaging in acts such as the seizing of buildings. The group wants Kiev to "be careful" as it relaunches its counterterrorism operation in the east, Ms Gorbunova said.
Among Horlivka's modest cohort of pro-unity leaders, the most pressing task is to uphold the rule of law and maintain peaceful political discourse in a region where the will of the mob increasingly prevails.
The town hall of Horlivka, population 270,000, was seized briefly on April 14 during a demonstration of about 1,000 pro-Russia separatists who named a "people's mayor" and raised the Donbass flag. The protesters left two days later and the city's elected mayor, Evgenyi Gleb, has since regained control.
Mr Rybak's death sent a chill through the city's pro-unity officials, who on Wednesday remembered the slain man as a passionate, at times impulsive figure who took part in many demonstrations and was unafraid of voicing his views. "He was a real 'oppositionist'," Mr Zhuk said. "He openly spoke out against power."
City councillors are split between those who support Kiev and those who favour a looser federation or closer alliance with Russia. They have left the Donbass flag untouched above the building since Mr Rybak's disappearance but business inside – unlike some other government buildings in the east – continues as usual, unimpeded by pro-Russia occupiers. Some councillors wear Ukrainian flag buttons on their lapels.
Townspeople have in some cases stepped in to defuse tensions in place of a police force they describe as demoralised, dysfunctional and split by the political issues of the day. In one recent case, when a member of a pro-Russian "self-defence" militia broke a woman's car window at a roadblock, it was ordinary citizens who stepped in to turn the man in to the police.
Amateur footage of Mr Rybak's abduction that surfaced this week show police standing by as the politician was shoved, pulled and insulted by the crowd before being hustled away by his assailants.
Oleg Gubanov, an independent councillor, said the city was still in control of its citizens. He said he had not seen a single Russian in Horlivka but "criminals" were making their way into the city.
"My personal opinion is that there is a third force that is trying to destabilise the situation," Mr Gubanov said. "What we need to do is find common sense."
Follow us on Twitter: @CNBCWorld