Both at fault in one way or another. Bottomline tho.....
Straightlining on a popsicle stick on anything but a closed course is negligent.
Its hard enough to control a good alpine board with sharp edges at those speeds, A park board with half the edges ground smooth has no chance of stopping or avoiding accident when the unforeseen happens.
That said, I always run interference for my kids by staying up hill and watching their six like an eagle. IF you straightline into my area you are gonna end up in a heap after launching off my shoulder pads NFL open field style. act negligently around me and endanger my children and I will treat you like a common mugger.