A helicopter ferrying a patient with a medical emergency from the Grand Canyon collided into another chopper carrying a patient near a northern Arizona hospital, leaving six people dead and critically injuring a nurse. The collision Sunday east of Flagstaff Medical Center was a few hundred yards away from a neighborhood that was spared the falling debris. Officials said they were unable to provide an account of what preceded the crash. Lawrence Garduno, who lives about a half mile from the crash, said he heard a loud boom that rattled the windows. He drove toward the hospital and stopped to see the burning wreckage. "It kind of scares me," Garduno said. "If this had happened a half mile closer, it could have fallen on our house." An explosion on one of the aircraft after the crash injured two emergency workers who arrived with a ground ambulance company. They suffered minor burns and were spending the night at the hospital, but their injuries were not life-threatening. The crash, about 209 kilometers north of Phoenix, also sparked a 10-acre brush fire that was contained. One of the helicopters was operated by Air Methods from Englewood, Colorado, and the other was from Classic Helicopters of Woods Cross, Utah. Both aircraft were Bell 407 models, said Ian Gregor, a spokesman with the Federal Aviation Administration.