On ending his trip to Mexico, a reporter asked Pope Francis what he thought about the Republican frontrunner. He responded by saying, “A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian.” Building a wall between Mexico and the United States, and making Mexico pay for it, has been a key talking point for Trump since the day he launched his campaign.

The New York Times reports that this came just hours after the Pope presided over a mass that exceeded 200,000 people in Ciudad Juarez, a border city. During his trip he also laid flowers at a new Rio Grande memorial to remember those who had died in their attempt to cross the border.

Trump responded in true Trump fashion by immediately going on the offensive. He accused the Mexican government of criticizing him to the Catholic leader “because they want to continue to rip off the United States.” He said that they should be ashamed of themselves for “using the Pope as a pawn.”

He even invoked ISIS:

If and when the Vatican is attacked by ISIS, which as everyone knows is ISIS’s ultimate trophy, I can promise you that the Pope would have only wished and prayed that Donald Trump would have been President because this would not have happened. ISIS would have been eradicated unlike what is happening now with our all talk, no action politicians.