I know Braddock's march was a year later.
In "Crucible of War", as I understand it, there are described several different witness's accounts, as to who shot first, and how that all came to occur.
There were three parties, the French troops, the Colonial troops under Washington, and the Native American forces with the Colonials, that were only partially under Washington's control.
The story I remember as the most striking was that Tanacharison, the “Half King, the Native American leader of the Ohio Iriquois, literally smashed the French Lt. Jumonville's brains out with a war club, the better to start a war between Britain and France, after the French forces surrendered to the Colonials.
I found it very hard to be certain what really happened that May day, and doubt that anyone ever will, as it was lost to history. Or covered up by some of the participants, perhaps, too.
I wonder, also, what verbal instructions Washington might have received from the Governor of Virginia before Washington departed for Pennsylvania, that were not recorded by history.