An investigation was underway into what killed a 22-year-old man who died on a flight from Dallas to Los Angeles.

The Los Angeles County medical examiner’s office identified the man as Rain McMillan Walmsey.

Walmsey was aboard Southwest Airlines Flight 958 on Friday.

According to the medical examiner’s office, the case remains open and the cause of death is deferred.

The flight was traveling from Dallas to Los Angeles when Walmsey suffered a medical emergency and stopped responding.

Crew members and fellow passengers attempted to save him, with multiple CPR attempts carried out while the plane continued toward Southern California.

Emergency responders were waiting for the aircraft when it landed at Los Angeles International Airport, but their efforts were unsuccessful.

Paramedics were unable to revive Walmsey, and firefighters pronounced him dead at the scene.

The circumstances surrounding the medical emergency remain unclear, and the medical examiner has not yet determined what caused his death.

Southwest Airlines previously confirmed that there had been a “medical incident involving a customer” aboard Flight 958 but did not provide additional details about the passenger.

The medical examiner’s office has now identified Walmsey, but the case remains open as officials work to determine the circumstances and cause of his death.