COEUR d'ALENE - A 44-year-old Seattle man competing in the swimming portion of this past summer's Ironman Coeur d'Alene didn't drown or suffer a heart attack, and he wasn't injured by another swimmer, a Kootenai County coroner document shows.

A coroner verdict document received Thursday through a public records request showed Sean Murphy was swimming in the June 24 event when his heart slipped into an abnormal rhythm, losing the necessary coordination to pump blood. He then lost consciousness.

Murphy died at 1:07 p.m. on June 26, according to the document.

His heart was resuscitated but he couldn't hold on and died of cardiac arrest at Kootenai Medical Center. He was resuscitated at the event's medical tent before being taken to KMC, where he was on life support until he died. Efforts to help him started out on the lake.

After losing consciousness in the water, he suffered what's called "hypoxic encephalopathy," which is an injury to the brain from lack of oxygen.

John Howard, a forensic pathologist for the Spokane County Medical Examiner's Office, said swimming possibly triggered the life-threatening heart rhythm. Murphy could have had a gene that made him more likely to suffer the abnormal rhythm, but it also could have happened spontaneously.

The medical examiner's office conducted the autopsy on Murphy.

In the coroner verdict document, Coroner Deb Wilkey specifically noted "prolongation QT syndrome."

According to the Mayo Clinic, "long QT syndrome" is a genetic abnormality in the heart's electrical system. It also can be spontaneous.

It affects one in 2,000 people, the clinic said in a July news release. It can cause a sudden fainting spell, seizure or sudden death.

Murphy's death is the first in 10 years of Ironman Coeur d'Alene.