The incident took place after four cars drove up to the checkpoint in Slavyansk, a city held by separatists, and began firing at its guards.
“They approached with their high beam headlamps on. Our man went to them and asked not to blind us, show IDs and open the trunk for inspection. Then an assault rifle got stuck out of the window and he was gunned down,” a witness told Kremlin-backed RT.
It's unclear who staged the attacks, but the shootings occurred just days after Geneva diplomats brokered an "Easter truce" between Ukraine government supporters and pro-Russian separatists.
“We thought nothing would happen because it was the holy night,” another witness, 62-year-old Yevgeny Bondarenko, told The New York Times. “Who can we trust now?”
The 26 militants guarding the checkpoint were carrying bats, not guns, in accordance with the terms of the truce.
Russian authorities blamed a far-right Ukrainian nationalist group known as the Right Sector for the attack, while Kiev authorities suggested that Russia had staged the violence.