An Orlando Police Department officer told him "active shooter, and he's still inside the building" as gunshots continued to ring out early Sunday. ... By the time I got almost to Orange, they came back on the radio: 'active shooter, still shooting.' Delgado was sure that when he arrived at Pulse nightclub, the situation would be over. "Usually, by the time I get to I-4 from here, they usually cancel it because they have all the people that they need. Suddenly, a tone came in from his dispatcher: Nearby Orlando police had issued a signal 43, an urgent alert that calls everyone from surrounding agencies into action.

Source: CNN June 17, 2016 12:56 UTC