Presumptive GOP presidential nominee Donald Trump has postponed his vice presidential announcement in the wake of an apparent terror attack in Nice, France, where a truck crashed into a crowd celebrating France’s Bastille Day, killing at least 60 people.

Trump was expected to announce Indiana Gov. Mike Pence (R) as his running mate at a highly anticipated Friday morning event in Manhattan. 

Reacting to the news earlier in the day, Trump tweeted, “Another horrific attack, this time in Nice, France. Many dead and injured. When will we learn? It is only getting worse.”

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Speaking on Fox News soon after reports of the attacks broke, Trump again chided President Barack Obama for not calling terrorist attacks “radical Islamic terrorism.”

“If it is indeed radical Islamic terrorism, it’s about time that he would say so, OK?” he said.

(At the time of Trump’s Fox interview, French officials had not officially concluded the attack was terrorism, and Obama had not yet spoken publicly about it.)

Trump also warned that “the world has got to strengthen up,” and suggested the U.S. should ban immigrants “from terrorist nations.”

“I would not allow people to come in from terrorist nations,” he said. “I would do extreme vetting. I would call it extreme vetting, too. And, you know, our country has tremendous problems. We don’t need any more of the problems.”

Later on Thursday, Trump again called in to Fox News to discuss the attack and create more suspense about his running mate pick, reiterating that he had not made “a final, final decision.” He also said he may cancel a scheduled appearance on CBS’s “60 Minutes” on Sunday, when he was expected to do an interview alongside his newly announced running mate.

Though multiple news outlets have confirmed that Trump offered Pence the vice presidential position, and the Indiana governor accepted, Trump would not confirm whether he has selected Pence, saying that he has yet to make a final decision.

It’s unclear when Trump plans to reschedule the announcement. Pence has until noon on Friday to withdraw his name from the ballot in Indiana, where he is seeking re-election as governor. State law prohibits him from running for governor and vice president simultaneously.