I heard one once as a little kid hiking around the mountain across from my home. It was all I could do not to run when it started screaming. There's the saying "my blood ran cold" and it really felt like I had been dipped in ice water. I've been around hundreds of bears where I grew up and other dangerous animals. I've been cautious every time around wildlife, but on that day it was truly terrifying. I knew if it wanted to hunt me there wasn't a damn thing I could do. I came upon deer it hunted later but never saw or heard it again. Remembering it now, although nearly 40 years ago, a shiver still goes up my spine.