In the early sixties I was at the San Francisco zoo, a place we went often, and quite near the polar bear exhibit, when the most incredible roaring started up! An error was made, and two male polar bears were released into the enclosure, and they attacked each other. I was a little kid and right there to see it. I still have the visual image of them both reared up and engaged and blood starting to show. We were near the exhibit when it started, but because of the incredible noise of the fighting bears, everyone in the zoo ran towards the enclosure to see. I remember my fear of all the people rushing towards me. My mother nabbed me and my siblings, and took us out the nearest exit which was near the aviary, if I remember correctly and up a pretty steep path. Never going to forget that! Sharp shooters were called in from the SFPD and killed one of the bears.