report runway incursion non-towered airport?

Joe Johnson wrote:

As I was on 1/4 to
1/2 mile final, the Citation suddenly took the runway and started the
takeoff roll;

I remember my first landing at a controlled airport with heavy iron.
(Got my primary training at a small grass strip.) I was told by the
tower to continue my approach. The runway was empty. But the very moment
I turned base to final, which is about 1/2 mile from the threshold at
that airport (Zürich), I saw to my surprize a 737 rolling onto the
runway and lining up, obviously cleared by the tower to do so. When I
was about 1/4 mile out, I got uneasy and called the tower, asking what
to do. "Continue approach, the airliner will depart." And so it did.
Plenty of room, a non event.

Stefan