Lester Holt

Dr. Todd Lukasiewicz, associate medical examiner for Allegheny County, performed the autopsy on Auden.

It was regarded as a sudden, unexpected death.

which meant the county needed to figure out why this otherwise healthy woman was dead.

There was no reason to suspect fertility hormones, vitamins or supplements like creatine could have led to her collapse.

Her brain showed no signs of a stroke, though an examination of the heart did reveal an abnormally shaped heart valve.

It's a congenital anomaly found in approximately 2% of the population.

Does it lead to early death?

Not in your 40s.

You need to be symptomatic.

At the conclusion of Autumn Klein's autopsy, the medical examiner was perplexed as to what killed this woman.

I'm not seeing anything.

I'm seeing a healthy white female that for all intents and purposes should be alive.

On the form that asked for cause of death, Dr. Lukasiewicz wrote, pending, no definitive answer.

But in a few days' time, he would have more information.

The blood work was back from the lab.

Autumn Klein had suffered a very unnatural death.

Coming up... What exactly had killed Autumn?

Or is the question, who?

When Dateline continues...

Two days after Allegheny County's associate medical examiner performed his autopsy on Autumn Klein, the phone rang.