If the kid was ultimately running away unarmed and he's got his hands raised and the cop is still firing away, then I'd say there's a problem.
If this witnesses testimony is anything approaching accurate, the cop used excessive force, albeit in the heat of the moment.
Once the unarmed kid failed to grab the gun (presuming he did attempt that), and then he ran, getting shot multiple times in the back (or front with hands raised) is going to be problematic.
This whole thing has been orchestrated. Their first attempt was Saint Skittles, but that one fizzled out.
The autopsy is going to be the first piece of actual evidence in this case. Everything else is words from people with axes to grind.