The incident took place around 6:20 a.m. near Somerville, about halfway between Memphis and the crew's destination of Bolivar.
Pilot Charles Smith, 47, of Eads, and two hospital workers, nurse Carrie Barlow, 43, and respiratory therapist Denise Adams, also 43, died at the scene.
The helicopter was on its way to pick up a boy who was in renal failure at the Bolivar hospital. They planned to take him to Le Bonheur, but the helicopter never reached the destination. Once hospital officials earned about the incident they arranged for the boy to be driven to Le Bonheur in an ambulance.
Officials say they still don't know what prompted the crash.
"They have taken care of so many kids in their short lives," Dr. Jay Pershad, medical director of Le Bonheur's air transport program, said of the crew Tuesday. "I can't tell you how incredibly difficult it is for the entire team."
The Federal Aviation Administration and the National Transportation Safety Board will continue to investigate the incident.
"It saddens me more than you can know. All three of these crew members were personal friends of mine," said company CEO Bill Conway.
This is the second crash in roughly three years for Hospital Wing, the air ambulance service that operated the helicopter. The company serves hospitals in Tennessee, Arkansas and Mississippi, transporting about 150 patients a month.