Well...I watched that video without sound, but it looked to me like the kid knew the mouse was going to get snatched...he had a very hesitant quality about him...the way you do when you know that the stove is going to light when the match gets close enough (wow...wasn't that a reference for the older posters) or when you're waiting for the eye doctor to blow air on your eye to determine internal eye pressure (again...probably an over 30 thing).
I think that was completely staged....
Not that you don't have to be aware when your chameleon is outside. You should be there.
I remember coming home to find my neighbor's canary sitting in her cage in the front lawn with a hawk sitting on the cage looking at her....
YIKES!!!!
My view is if the humans who made them captives are not there to ensure their safety, they should not be left vulnerable.
So, let him have an outdoor experience, but be there. If you have aggressive birds in your neighborhood, carry a broom to whack them.
Long ago, I had to stand guard over my family dog when she went outside...there was an angry blue jay who would attack her...everyone in my family was tasked with taking a broom and standing over the dog as she did her business...I personally whacked that bird at least 20, 30 times.
The bird always came back, so we obviously never hurt it...but we kept it from hurting the dog, which was the important thing. And, there's absolutely no way your chameleon will need to "go outside" as often as our dauchshund did.