"It simply proves that more than one professionally trained group was shooting at the demonstrators."
Follow the money. My guess is that however many groups were there and firing on protesters the money for them all flowed from the same source.
The Russians would be stupid not to fund an anti-Russian group that advocated shooting pro-Russian protesters and the EU/US would likewise be stupid to not fund a pro-Russian group committed to shooting anti-Russian protesters. Such groups being active doesn't mean they're funded by and approved of by those they are most logically tied to.
"The eye witness mentioned in that leak was the same Olga Bogomolets that is now pointing at the Russian Federation's Alfa units."
That queers the story somewhat IMHO. Changing stories are noise, not information.
In the "Information Age" when there are so may 24/7 mouths to feed it's easy to get various news hungry outlets hooked on a source and spread disinformation through them and equally easy to get stories intended to undermine a worthwhile source spread.
I don't know a source I can trust there so I suspect all of the groups equally of planting whatever they think will help them and hurt their opponents. I also believe every group involved is ready, willing, and able to carry out targeted killings when it serves their purposes including both the US/EU and Russian supported factions.
The only thing I know for sure is that no strong Ukrainian leader capable of bringing any order to the Ukraine has emerged and there doesn't seem to be any such leader on the horizon. Barring a such a leader appearing, the Ukraine is the 2014 replay of the collapse of Yugoslavia. Russia has already taken what it saw as the most important part of the country ensuring that the infrastructure there will be spared should NATO decide to use air-strikes in support of a particular faction if serious fighting starts. Whether it wants more remains to be seen.
If Russia does want more, I believe it'll drop in their lap without any further military action beyond posturing. The EU and the US are absolutely not going to back a Ukrainian leader they can't totally control, so, the EU and the US are going to negotiate until the cows come home or the Ukrainians start killing one another with gusto.
JMHO
Somebody shot a pro-Russian protester? Where? When?
Changing stories
Bogomolets did not change her story. She witnessed shots coming from "both" sides. That means, there was Berkut firing and Alfa firing and naturally, firing from two different locations.
The Soviet press picked it up and made it sound that "sides" meant "political sides". But a nurse during the battles thinks of shot directions, not political sides. That is what she meant then and confirms now. The whole idea that somehow the revolutionaries would shoot themselves and get paid for it is a product of sick Soviet minds, and it is not borne out by facts.