Having trouble removing movieClip

I have trouble getting to it…

this works fine:

holderArr[loadedImages].preloader_mc.stop(); 

this works fine:

trace(holderArr[loadedImages].getChildAt(3).name); 

output: preloader_mc

but if I say this:

holderArr[loadedImages].removeChild(preloader_mc); 

I get an error:
ReferenceError: Error #1065: Variable preloader_mc is not defined.
at MethodInfo-84()

this doesnt work either:

 holderArr[loadedImages].removeChild(getChildByName(preloader_mc));

nor this:

 holderArr[loadedImages].removeChild(getChildByName("preloader_mc"));