“I am extremely, extremely tough on illegal immigration. I’m extremely tough on people coming into this country. I believe that if I were running things, I doubt those people would have been in the country,” Trump said on “Fox News Sunday.”

“With that being said, I’m not blaming George Bush. But I don’t want Jeb Bush saying, ‘My brother kept us safe,’ because Sept. 11 was one of the worst days in the history of this country.”

Bush fired back, saying the real estate mogul’s comments about the Sept. 11 attacks show that he is not serious about being commander in chief — the central theme of his new Web ad attacking Trump.