Sad. The only appropriate response is to tell Trump and his GOP toadies to get over it. This is the situation they created. This is the natural consequence of reactionaries and lax gun control. They shat this bed and they absolutely deserve to drown in it.
The best response is exactly his response. He's better then Trump, so he acts like a better person by not saying stupid shit like Trump does. Although I'm sad the shooter missed, political assassination is always bad, and likely will work in Trump's favor. If Trump would have died, another even more radical replacement would have benefitted from it. There is no positive outcome from a political assassination. Trump will either get more support or become a martyr.
But just like usual, they'll lie, take no responsibility, and say they had absolutely nothing to do with inciting violence and hatred like they have for so many years and just blame Democrats for it.