Michael David Wilson, 49, was a trauma patient at Choctaw Nation Health Center and was being taken to Tulsa. He was pronounced dead at the hospital.
"It happened upon take-off," said David Wharton, a spokesman for Choctaw National Health Services, "literally yards from our emergency department."
A nurse aboard the flight was critically injured and taken to Saint Francis Hospital in Tulsa, where her condition was upgraded to serious but stable. The pilot, Kip Sorensen, and paramedic Ryan Setzkorn were treated and released.
The helicopter was a Eurocopter A Star B2 dispatched out of McAlester.
Emergency responders said they had to contain leaking jet fuel to prevent a potential explosion, said Wilburton Fire Chief David Donoley, who was on the scene.
The crash was the second involving an EagleMed helicopter this year; two people were killed in a crash in February in Oklahoma City.
Robbie Copeland, spokesman for EagleMed, said the crash would leave the hospital temporarily without the services of a medical helicopter.
Investigators from the Federal Aviation Administration and National Transportation Safety Board were on scene Wednesday to begin determining what caused the crash.