BUCHA, Ukraine—In early March, Volodymyr Borovchenko walked uphill on Yablunska Street to get to his job at a home for special-needs children—and straight into a Russian military no-go zone.

Russian troops, halted in their advance on Kyiv by Ukrainian forces, had occupied Bucha days earlier. Telling local residents they were worried that somebody was reporting their positions to Ukraine’s military, the Russian soldiers ordered people to stay off the street, which runs parallel to the Bucha River on the southern edge of town.