During many years of CW re-enacting, I saw darned near
everything you can send downrange done so. I've heard horror stories of premature ignition and hands flying into opposing ranks. I just hope they were only stories. I do recall as a kid seeing what I thought was a rammer from a rifle sent into a group of people but never heard if I'd seen that correctly or not. Thankfully, where we did most our events, only one guy per unit was allowed to carry a ramord with their rifle just in case it was needed. In the NE, I have seen events where everyone had them. I know at Gettysburg in 1998, at least one went downrange but didn't hurt anyone.
Turns out, a guy I went to college with (I majored in communications and interned with a newspaper) e-mailed me not too long ago, saying he'd worked on this and other projects for the production company that makes many of these kinds of shows. Among other things like saying he'd seen Johnny Knoxville's junk get crushed (you're better off not knowing the story. Trust me), he mentioned this episode. I e-mailed him asking if he'd seen this done. Yesterday he e-mailed back saying he was there, they did fire the projectile into the treehouse and surrounding trees, it's just that it wasn't done quite the way they showed it, as he's adamant they never fired over the heads of people downrange.
So at least
someone had a brain that day, it seems!