Understanding what causes an overwhelming fear response in a dream can help you understand that there is literally nothing to fear. I've done a lot of research on the science of sleep and dreaming, and I can tell you this:

What's responsible for overhwelming terror and aggression is a part of the brain called the amygdala. It's what's responsible for the fight or flight response, a very primitive and powerful system that can help get us out of harm's way or spur us to take action when it's needed rather than standing like a deer in the headlights when danger is near. From time to time during sleep the brain sort of test-fires some of it's systems just as a maintenance check to make sure they're still fully functional, and when it runs a diagnostic on the amygdala that's when we have nightmares of primal terror or aggression.

Apparently your lucid experience happened to coincide with this diagnostic test - no telling why. But it was nothing more than a sort of fire drill.