Employing the same tactics of fear that he used to win 2016, Trump has encouraged public fear for political gain. See his Churchillian tweets below.
This was in response to the mayor of London notifying the public to not be alarmed to the increased police presence resulting from the recent attacks.
It would be assumed that proper leadership would reassure during a crisis, but the new normal in America is prepetuaing fear, whether of Mexicans, Iran, healthcare, or even Skittles.
These are sad times for America.