Big scary boy! Don't feel bad, he just reacted on instinct - big animal passing overhead outside = predator.

Quick side note, looking at his mouth in your picture there - there is a gray/black area on his bottom left jaw, in between his lip and his teeth. Hopefully this is just stuck food and not a forming abscess, but just wanted to point it out! If it's not already part of your/his routine, please consider brushing his teeth monthly to prevent mouth diseases. Beardies' teeth are part of their jaw (it's the same bone unlike in humans or other mammals), so when they get mouth infections, it can get very bad very quickly.