I would believe the Rangers do that with the bears. We came across a bear next to the road that was fishing in a small body of water. He was about 50 yards off the road and on all sides the water was surrounded by trees. Within 10 minutes traffic was backed up for a mile in either direction. After about ten minutes the bear suddenly bolted from the water and climbed a tree, just like something was after him. He then jumped from the tree and ran away. The action was out of character for what he was doing and I thought at the time that possibly a ranger had worked his way around and possibly shot him or startled him some how.
The wolves we saw last year were always on a dead run whenever they got close to the road. I have heard from others the rangers do shoot the wolves with rubber bullets to keep them scared of humans.
But it just isn't bear and wolves that are dangerous. Elk have little or no fear of any one, in Mammoth you can get just a few feet from one.
I took a run down to the Tetons and came across a very large Bull Moose close to Jackson Lake Lodge. There were 100 or so people with one ranger watching it eat, within 20 yards. The rangers do more people control than they do animal.
Point is the wildlife in these two big parks, really aren't what I would consider wild. The real danger to people is there own ignorance, because they can get that close to these big animals they think it is ok to get even closer.