As the shooting occurred right outside the ballroom and the positioning of all LE (and Doocy reports SS was the Hawkeye team which is generally involved in extreme situations)- and the search through the ballroom - yes there were probably multiple aggressors involved.

But just like with every PHUCKING thing else from the Las Vegas Shooter to Kirk to the many many many events through history - we will be told there was ONE - and 'nothing to see here so move on'. No other threats (my azz).