Bison in rut are extremely unpredictable and can be ridiculously aggressive. Something about the truck going by set him off and he went after the closest thing. Can't blame grandpa but also, you can never underestimate the speed, power, and agility of a bison, They are not cows.
Don't mess wirh the bull, young man, you'll get the horns. Entitled park visitors think that they're at a petting zoo, despite constant reminders from the park rangers that the wild animals are, in fact, wild, and thus dangerous. I totally blame grandpa for walking around with 0 cares within the charging distance of an enraged bison. Its been decades, but when I was at Yellowstone as a child, my grandparents made sure I didn't get anywhere remotely near the bison, even when they seemed calm and peaceful. Especially when it starts rolling around on the ground, that bull is pretty clearly agitated. Old guy maybe sensed a little danger a few seconds too late and started walking for cover just a little too late. But better than his son/grandson who just stands there. Old man decided to f around, and the bull helped him to find out. There is no way I'd get that close to a bull giving off that much "im upset" energy without a car as a barrier. Just googled and BY LAW the closest you can get to a bison under the best of circumstances at Yellowstone is supposed to be 75 feet. If the start the encounter more that 75 feet away, it's not by much.
To be fair it just seemed like he was walking in the park and saw a bison over by a picnic table. Why are there picnic tables if you aren't safe walking to them? It's not like he even walked towards the bison. I wonder where the people went who had that picnic spread on the table. Did they run for their lives? Haha
