The Associated Press reported around the same time as Trump's remark that firefighters were at the scene of a possible building explosion in the city.
Trump added: "But boy, we are living in a time -- we better get very tough, folks. We better get very, very tough. We'll find out. It's a terrible thing that's going on in our world, in our country and we are going to get tough and smart and vigilant. ... We'll see what it is. We'll see what it is."