Six people died Sunday night when the deadliest single tornado in modern U.S. history smashed into a hospital in Joplin, Mo.

The 367-bed St. John's Regional Medical Center suffered extensive damage as the twister struck it head on. The tornado, rated an EF-5 storm by the National Weather Service, had winds in excess of 200 miles per hour.

Witnesses said the twister, which sounded like a freight train, blew out windows, obliterated the emergency room and sent gurneys soaring blocks away. X-rays and other medical records were tossed dozens of miles to neighboring counties.

Hospital staff were able to evacuate 183 patients. Five patients died after their ventilators lost power, and a visitor was also killed, according to media reports. But all 175 staffers in the hospital at the time of the storm survived.

A school nurse from Wichita, Kan. took pictures of the interior of the hospital, showing hallways littered with glass from blown-out windows and other debris.

At last count, the tornado has claimed at least 125 lives in Joplin, a town in the southwest corner of Missouri. The twister is considered the deadliest since the National Weather Service began tracking such storms in 1950.