Using getChildAt with a sprite conatiner is removing a child from the container

I am trying to get an image object from one sprite container and adding it to another sprite container. But when I use GetChildAt for this, it will remove the object from the parent sprite and place it inside the other.

Code:
sprContainer1.addChildAt(sprContainer2.getChildAt(1),0);

Problem is when I run this code sprContainer2.numChildren is getting reduced by 1, which seems that this code removes a child from sprcontainer2. any thoughts why this is happening?