In 1999, tornadoes killed 94 people in the United States, according to the National Oceanic and Atmospheric Administration. Every year, hundreds of tornadoes touch down in this country. CBS News' 48 Hours takes a close-up look at this powerful and often terrifying force. A 300 MPH Monster: Correspondent Peter Van Sant reports on the killer tornado that struck Oklahoma in 1999. He focuses on two families, the Tinnemans and the Darnells, who were hit with almost no warning. Afterward, A Paramedic Works Alone: When the tornado had done its damage, a lone EMT found himself treating a gym full of badly injured people. Among those people were members of the Darnell and Tinneman families. Looking For A Stormy Vacation: Correspondent Harold Dow reports on a group of vacationers who spend their time off looking for very bad weather. A Tornado-Sensing Dog: Richard Schlesinger reports on a dog that helped save his owners from an approaching tornado.