A massive tornado ripped through Joplin, Mo., Sunday, May 22, 2011. The Red Cross estimated as much as 75 percent of the town was leveled.

photo by: Mark Schiedelbein/AP Photo

Emergency personnel walk through a neighborhood severely damaged by a tornado near the Joplin Regional Medical Center in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging a hospital and hundreds of homes and businesses.

photo by: Mark Schiedelbein/AP Photo

Destroyed vehicles are piled on top of one another in the parking lot of the Joplin Regional Medical Center in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging the hospital and hundreds of homes and businesses.

photo by: Mark Schiedelbein/AP Photo

People walk down a street lined with destroyed homes in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging a hospital and hundreds of homes and businesses.

photo by: Mark Schiedelbein/AP Photo

Rescuers and neighbors look through the the wreckage of destroyed homes on a hillside in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging a hospital and hundreds of homes and businesses.

photo by: Mark Schiedelbein/AP Photo

A man walks past destroyed vehicles in the parking lot of the Joplin Regional Medical Center in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging the hospital and hundreds of homes and businesses.

photo by: Mark Schiedelbein/AP Photo

A destroyed helicopter lies on its side in the parking lot of the Joplin Regional Medical Center in Joplin, Mo., Sunday, May 22, 2011. A large tornado moved through much of the city, damaging the hospital and hundreds of homes and businesses.