His comments after the Kirk assassination were kind and gracious, out of step with the rest of his ideologue compatriots
Charlies murder was political
Reiners murder was not political though Trump classlessly tried to make it so
Trump missed a chance to be great here by simply acknowledging sympathy to the surviving family ( Michelle Reiner was a talented photogapher who produced Trumps cover photo on his first book) and bringing the horror of drug addiction and its destructive results into the public dialogue
I can't find anything, and it would be amazing to find out that he took the opportunity to say nothing.
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I suspect... that is exactly how Reagan would have handled it. But then... the radleft never put Reagan through what they have put Trump through, so there's that.