The aircraft were each carrying patients to Flagstaff Medical Center and went down Sunday at 3:49 p.m. on McMillan Mesa about a half-mile east of the hospital. Classic Lifeguard Aeromedical Services of Page operated one of the copters. The other copter was part of the Guardian Air Transport of Flagstaff. Guardian Air is a division of Flagstaff Medical Center.

The crash is believed to be the single worst air disaster inside the city of Flagstaff. Killed were both pilots, along with a flight nurse/paramedic, a flight medic and the two patients the flights were transporting to FMC.

The sole survivor of the crash, James Taylor, 36, the nurse on the Classic flight, remains in critical condition this morning at FMC.

The victims were identified as:

— Pat Graham, 50, Guardian pilot

— Shawn “Clyde” Shreeve, 36, Guardian flight nurse/paramedic

— Raymond Zest, 54, patient

— Tom Caldwell, 54, Classic Lifeguard pilot

— Tom Clausing, 36, Classic Lifeguard medic

— Michael McDonald, 26, patient

An exploding fuel tank in one of the aircraft slightly injured two ground ambulance workers and touched off a 10-acre wildfire that was extinguished by local firefighters.

The Classic flight had a crew of three and was bringing in a patient from the Grand Canyon’s South Rim. The Guardian copter was bringing in a patient from Winslow.

An FMC official said the hospital owns the aircraft and provides the medical personnel on Guardian flights, while Air Methods provides the pilot and maintenance.

Bill Summers witnessed the Sunday accident from his home at Lomalai Lane and Forest Avenue.

He was watching one of the helicopters approach the hospital for a landing when he saw the second helicopter.

“He was coming in from the south, low and fast, and I said what the heck is going on here — they are going to hit each other,” Summers said.

“About that time the one coming in from the south went under the other one and there was an explosion.”

The FMC helipad remains open, but Guardian flights are not operating today.

National Transportation Safety Board spokeswoman Bridget Serchak said today that agency investigators were expected in Flagstaff by 8 a.m. Arizona time.

NTSB teams typically issue a preliminary report that includes only the general facts surrounding the crash. A full report that describes the cause of the crash usually comes within 12 to 18 months.