Found this article I thought was interesting,
http://query.nytimes.com/gst/abstract.html?res=9E0CE6D81F3FEF3BBC4151DFB467838B679FDE
The S.C.M. had been ordered to peacefully occupy Castle Pickeny & Fort Moultrie for protection of government property. I was gonna copy the inage and try to post it but the site wouldn't let me. Guess I wore out my welcome there.
clearly states Anderson did ask for reenforcements to occupy the forts in Charleston, and this request was known by South Carolina. I believe that may have been the reason they moved on some of those federal installations even if Sumter was the commanding fort for the harbor.
These actions sort of remind me of the Cuban Missile Crisis. Nobody wants a hostile force at their door.
GP