Only Governments have helicopters of any size to carry men....
If it is unmarked, hhmmmmm,,,it is likely Russian...Right?
The Russians are claiming its the Ukrainians. They have a picture of a Ukrainian helicopter at the link, but not the one that they are claiming carried out an attack.
“A Ukrainian military helicopter flies near the village of Malinivka, east of Slaviansk in eastern Ukraine April 25, 2014 (Reuters / Baz Ratner)”