Video shows bear eating picnic: “The real bear is the mother who protects her cub”. By slowly backing away, you signal to the bear that you don't want to harm it.
Don't surprise or provoke the bear! You should make yourself noticed as early as possible by speaking loudly. Keep calm! If the bear is not yet too close, stay as far away as possible and under no circumstances try to approach it. Do not attempt to take photos or track the bear, instead use this time to get out quickly.