It's a bit surprising that something like this didn't start happening sooner. It's not as if one can expect to mosey through the territory of large intelligent land predators completely unassailed.
Well if you're in a vehicle you can. I suppose the equivalent of this would be a rash of rural road incidents with grizzly bears attacking cars.
I thought territoriality was more a thing for "peer" sizes. Adult lions don't chase mice for invading territory. And while foxes may be highly territorial they aren't stupid enough to try to attack say a bear for invading.