Fortunately, eagle cam fans who had been watching around 2 a.m. (central time) reported that the three eaglets are fine. When the owl started hooting, Mom and Dad did a great job of basically warning that "you'd better stay away."
The owl never did swoop in to try to snatch the babies.
One eagle cam fan captured about 5 minutes of the action and posted it on YouTube. The eagles are quite vocal (there is a buzz in the audio, but it doesn't take too much away from the drama).
As the YouTube poster says, if you fast-forward to the about the 4:27 and 4:52 marks, you can hear the owl calling back.
Note: If the eagle cam page doesn't come up for you right away, don't get discouraged. Come back later and try again. Its always worked for us after a few tries.