Not sure which bumblebee species we have that is aggressive, but every so often we bump into a "ground bee" that is very defensive of the area around their hive. We have multiple species of bumblebees here, so I don't know if it is just one species that is aggressive, or if it is like honey bees and some hives are aggressive. And maybe it is during drought that they act this way.
I have found several while on tractors, one while on a 4 wheeler, and 2 from pickups. I would rather have 5 honey bee stings than one of these. They physically hit hard and then you feel the intense sting. And they can come in numbers. It is cool to hear honey bees bumping windows when mad, but it is sort of intimidating to hear these guys do it.
Zbee - So I would mark that nest and give it are rather wide berth during drought. I love the bumblebees but darn they hurt.