But until he actually KILLED someone, they were powerless to act...
Exactly
Can't act until a crime has been committed.
The answer?
Don't allow them in the Country in the first place ! Duh !
I wonder how many of these warnings they get. It’s one thing to flip out that “they were warned and did nothing” if they only get a few warnings and they’re all serious, it’s quite another if they get 1,000,000 warnings and most of them are garbage.