Why should Americans be shaken to their very core?
Roof did what the Left has been moving toward for the last 25+ years—Elimination of Christians.
The Left is shaken only because the nutball let the cat out of the bag ahead of schedule.
....Or they (the left) in private clapped their hands to what this demons controled shooter did, created new Christian martyrs. This simply planted more seeds to create new Christians in the process.
For a brief moment before he was ID’d the Left had to be peeing their pants worrying that the perp here might have been a Muslim.