UPDATE: Trump delaying running mate announcement

WASHINGTON (AP) — Donald Trump abruptly postponed plans to announce his vice presidential pick after a day of rampant speculation, citing the "horrible attack" in Nice, France, that left scores dead.

Trump had planned to hold his first event with his yet-to-be-named running mate Friday morning in New York. He announced the change of plans tonight on Twitter.

The stunning announcement raised questions about the status of Trump's selection process. Indiana Gov. Mike Pence had emerged as a late favorite for the job, though Trump said he had not finalized the pick and advisers cautioned he could change his mind.

"I haven't made my final, final decision," Trump said on Fox News.

After spending much of today in Indianapolis, Pence flew to New York late in the day, according to a Republican familiar with the process. Indianapolis television station WTHR posted a video showing Pence arriving at a private airport in New Jersey early this evening.

Trump did not say when he planned to announce his running mate. He's up against a clock: The Republican convention kicks off in Cleveland Monday.