[Clay Moore]

“What's your best guess? “

They were under FBI surveillance. Neither knew they were present and the FBI held people back and let it happen so as to not spook them.

Many years ago, we could bounce a laser off of a window and monitor the conversations going on inside. Surely technological evolution did not stop there.

[Elsie]

Many years ago, we could bounce a laser off of a window and monitor the conversations going on inside.

We still can!

But a window shaker can pretty much overwhelm the small vibrations that voices would cause on the glass.

But... http://www.pimall.com/nais/n.lazer.eaves.html