Specifically, the cause of death was high altitude cerebral edema due to acute high altitude sickness, according to the Siskiyou County Sheriff's office.
"In laymen's terms, it's when your brain swells," said Sgt. Mark Hilsenberg, who added that their office is still awaiting toxicology results to rule out any other cause of death.
Bennett, 26, was hiking on the mountain with his friend, Mark Thomas of Berkeley, also 26, when the two experienced climbers hit bad weather and were forced to stay the night near the 14,050-foot summit.
Thomas made it down by Monday, but Bennett was suffering symptoms of altitude sickness and was unable to make the climb back down the mountain. Thomas had to make the tough decision of leaving his friend behind in a snow cave while he sought help.
But the weather was too severe for rescuers to search for Bennett until last Thursday when they discovered his body in the snow cave, which Thomas had marked.
High altitude cerebral edema causes brain swelling because of fluid that leaks into the brain tissue, said Hilsenberg. Preliminary symptoms include nausea, vomiting, confusion, and finally, coma. If sufferers aren't removed from high elevations right away, said Hilsenberg, the results are "very fatal."
Even experienced climbers like Bennett who have been at similar altitudes and never experienced the same symptoms are vulnerable to a quick onset of severe altitude sickness, Hilsenberg said.
"You could be the fittest person in the world," he said. "Human bodies are very fragile."
Bay City News contributed to this report.