My wife says "it looks like they murdered a small animal on the deck!" Yes, it certainly does! Obviously my children did not murder a small animal (I hope), so what did they do? Their grandma gave them a set of colored snow 'paint' for Christmas. They each received an empty squirt bottle-like container along with colored powder that you mix with water to make liquid snow paint.
My daughters had a blast coloring the snow and then mixing it all around. The colors they chose on this day were red and orange, hence the "bloody" deck. No bones or animal carcasses were found! LOL!