The closest thing like that that happened to me when I was about 16 years old and I was on a trip up in Alaska. We were fishing the Salmon run and out walked momma Griz about 150 yards up stream. That was a oh crap moment. At least there were 10 of us or so but we still high tailed it out of there and hopped in the Kayaks.... With Black bears we would bang pots and they would go away, the big fellas though.. Not risking antagonizing them...

And once in Montana while hiking I saw a cat stalking my dog. I was about 100 yards (west) behind the dog, trying to catch her becasue she had taken off after something and the cat was up top on a ridge line, maybe hundred yards (South) from the dog. Picked up a branch and banged into the tree. Cat saw me and took off. Dog came back finally and again, we left. Never went out in the woods without a large handgun again in Montana. There were quite a few hunters out there who had close encounters of the Grizzly kind. ESP bowhunters.