@ZiSs: While the reports say that the vehicle on the left was in fact Ukrainian and the vehicle on the right Russian it has to be said that no markings indicating either side could be seen on each of the vehicles.
Some argued that the MRAP was in fact a Ukrainian MRAP and the Strela-10 was captured by Russian forces who , what reports claim, got caught operating while wearing Ukrainian uniforms and driving Ukrainian vehicles.
Also a friendly fire incident between Russian forces due to this fact and bad communication can be possible.
Also a friendly fire incident between Ukrainian forces is possible.
Due to the bad quality of the footage and a lot of conflicting information there are 4 possibilities here:
1. Russian MRAP Engaging Ukrainian Strela-10
2. Friendly fire incident between Ukrainian troops.
3. Ukrainian troops engage hijacked Strela-10
4. Friendly fire incident between Russian MRAP and hijacked Strela-10