What became known as “the first Soviet conquest of the Ukraine” was achieved without much resistance. The Ukrainian soldiers who had pledged allegiance to the Rada in summer 1917, while still part of the Imperial Army, were now back in their villages. Petliura had poorly trained men at his disposal, mostly the so-called Free Cossacks (Vilne kozatsvo), some of whom found the Bolshevik appeal more attractive and changed sides. In abandoning the city, Petliura’s followers not surprisingly had executed as many of the renegades as they could get their hands on. Once in possession of Kiev, Colonel Murav’ev introduced his own reign of terror.
That is from Laura Engelstein, Russia in Flames: War, Revolution, Civil War 1914-1921, which is in general a very useful book.