"When he heard the first scream in a campground outside Yellowstone National Park, Don Wilhelm thought it was just teenagers, maybe a domestic dispute in the middlle of the night. The wildlife biologist from Texas tried to go back to sleep, stifling thoughts that a beast might be lurking outside his family's tent. Minutes later, another scream — this one coming from the next campsite over, where a bear had torn through a tent and sunk its teeth into the arm of the middle-aged Canadian woman inside. ""First she said, ""No!' Then we heard her say, 'It's a bear! I've been attacked by a bear!"" said Wilhelm's wife, Paige. By that point, the bear already had ripped into another tent a few campsites away, chomping into the leg of a teenager who had been sleeping with his family. Wilhelm later would find out that a solo camper at the other end of the heavily occupied Soda Butte Campground had been killed in a rampage Wednesday that one wildlife officials described as the most brazen bear attack in the Yellowstone area since the 1980s. But in the pitch-black wilderness, the Wilhelms had only sounds to go on: The yells from the teenager and his sister, the Canadian woman's screaming of ""No!"" as she was attacked, the snorting and huffing noises from the bear as it sniffed around thickly forested campground. And then, finally, quiet."