A medical helicopter crashed in rugged terrain east of Phoenix, killing two crew members and seriously injuring a paramedic who was still able to use a flashlight to signal search aircraft, a sheriff reported Wednesday.

Pinal County Sheriff Paul Babeu said the helicopter crashed Tuesday evening on a cliff or mountainside about 12 miles north of Superior, a mining community outside Phoenix.

Air Methods, which owns the company operating the aircraft, said the chopper was also carrying pilot David Schneider, 51, and nurse Chad Frary, 38. It's not clear whether the crew was transporting any important medical items such as organs.

The surviving paramedic is 38-year-old Derek Boehm, according to Air Methods.

Babeu said an aerial search began after the helicopter was reported missing around 6 p.m. and that he knew of no radio transmission from the aircraft before it went down or any report from the public about a crash in the Tonto National Forest. The helicopter was flying from a Mesa airport east to Globe.

An Air Force helicopter rescued the injured survivor from the crash site in rugged terrain about four hours after the crash and about two hours after the wreckage was first spotted by search aircraft. The paramedic was rushed to a trauma center in the Phoenix area in "very serious, critical condition," Babeu said.

A Native Air helicopter first spotted the wreckage at about 8:30 p.m. and an Arizona Department of Public Safety helicopter located it about a half-hour later, but neither was able to land because of rugged terrain.

"From what I understand it's in a precarious situation," he said of the crashed helicopter.

The crash scene was sealed off overnight to preserve evidence before National Transportation Board Safety investigators arrive later Wednesday, Babeu said.

The Associated Press contributed to this report.