The fighters, members of the Donbass People's Militia, later captured the police station. They removed the police station's sign and raised the flag of the Donetsk People's Republic over the building. They then issued an ultimatum that stated that if the city's mayor and administration did not swear allegiance to the Republic by the following Monday, they would remove them from office. Concurrently, a crowd of demonstrators surrounded the city administration building, captured it, and raised the Donetsk People's Republic flag over it. A representative of the Republic addressed locals outside the occupied police station, but was received negatively and booed. After a government counter-offensive as part of the "anti-terror" operation in Donetsk Oblast on 2–3 May, the insurgents were routed from Kramatorsk's occupied SBU building. Despite this, Ukrainian troops quickly withdrew from the city for unknown reasons, and the separatists quickly regained control. Sporadic fighting continued until 5 July, when the insurgents withdrew from Kramatorsk. Militants attempted to seize the police headquarters in Horlivka on 12 April, but were halted. "Ukrayinska Pravda" reported that police said that the purpose of the attempted seizure was to gain access to a weapons cache. They said that they would use force if needed to defend the building from "criminals and terrorists". By 14 April, however, militants had captured the building after a tense standoff with the police. Some members of the local police unit had defected to the Donetsk People's Republic earlier in the day, whilst the remaining officers were forced to retreat, allowing the insurgents to take control of the building. The local chief of police was captured and badly beaten by the insurgents. A Horlivka city council deputy, Volodymyr Rybak, was kidnapped by masked men believed to be pro-Russian militants on 17 April. His body was later found in a river on 22 April. The city administration building was seized on 30 April, solidifying separatist control over Horlivka. Self-proclaimed mayor of Horlivka Volodymyr Kolosniuk was arrested by the SBU on suspicion of participation in "terrorist activities" on 2 July. Donetsk People's Republic activists took control of the city administration building in Mariupol on 13 April. The Ukrainian government claimed to have "liberated" the building on 24 April, but this was denied by locals interviewed by the BBC near the building. Clashes between government forces and pro-Russian groups escalated in early May, when the city administration building was briefly retaken by the Ukrainian National Guard.