Three other skydivers who jumped with them told investigators that equipment appeared to malfunction, Rigel said Sunday.
"They said something appeared to be not right. There appeared to be some entanglement with the lines, but I'm not qualified to say what that was or even speculate about it," he said.
Federal Aviation Administration inspectors will look at whether the parachutes were properly rigged by a qualified rigger and whether the parachute operation met FAA regulations, but local authorities will investigate the accident and determine probable cause, FAA spokeswoman Kathleen Bergen said in an email Sunday.
The sheriff's office was called at 1:40 p.m. Saturday, more than 3 hours after the jump, Rigel said. He said he did not know the reason for the delay.
The owner of a hunting lease for the area found the men, and the student was taken to Forrest General Hospital. A nursing supervisor there said the family had not authorized release of any information about him.
An autopsy is planned for Horak, probably Monday, Rigel said.
"We had to hand-carry him out. We still don't know what the cause of death was or what caused the malfunction," Rigel said.
Debbie Horak said she and their three children were waiting for autopsy results to find out what happened to her husband, a full-time physician's assistant and part-time pilot and skydiving instructor.
"My husband is a very, very skilled skydiver. Very safety-conscious," she said.
She said he had no medical conditions and described him as healthy.
"He liked adventure, but very much a Christian and family man," she said.