The Ohio National Guard didn’t “open fire” on the crowd.
Words mean things, so let’s not use them improperly.
Leave that to the left.
The grammatically correct phrase would be to say that The Ohio National Guard returned fire coming from somewhere in the crowd.”
While this was a topic of dispute for decades, modern forensic analyses of the recordings of the event have effectively ended the discussion.
the article I linked indicates where the initial shots may have originated.