Two friends spent a summer afternoon

ski shooting in rural Pennsylvania.

Only one returned home.

The other died of what was determined to be an accident.

What happened that day sent shockwaves through a small town

and launched a mystery that would take 20 years to solve.

Montrose is a quiet rural area in the northeastern corner of Pennsylvania.

It's a small, close-knit community with stately homes, one traffic light,

and the courthouse that dominates the town square.

In 1976, Montrose was home to 30-year-old Martin Dillon,

his wife Pat and their two young children.

Marty Dillon was a very popular man in town,

and his father was the local mayor.

Everybody knew him and really liked him.

On June 2nd, 1976, Martin Dillon left work early to go ski shooting

at his family's hunting camp, a secluded place called Gunsmoke.

His good friend, Dr. Stephen Schur, went along.

Stephen Schur was one of the town's doctors and a close personal friend of the Dillon's.

Martin asked some other friends to go with him that day,

but they all had other plans.

And I said, Marty, I can't go on.

I said, I got just so much going on.

...