Moments before images of frightened students captured the scene, audio from the emergency radio system recorded its chaos.
But mixed into the high octave chorus of emergency response, you can hear unexpected challenges police and fire rescue crews in Broward County couldn't hear coming.
"Bravo 2-3, we're having trouble communicating," said an officer in an excerpt pulled off of broadcastify.com, a website that tracks and records radio scanner traffic among emergency crews.
The radio system police and rescue crews used to communicate was overloaded leaving crews unable to talk to each other during some of the earliest moments of response from the Broward County high school shooting.
"Attention all units, keep your radio traffic to an absolute minimum due to overload," a dispatcher can be heard saying.
"Be advised our radio might go down."
Bruce Moeller is a former Florida Fire Chief and City Manager, today he's a public safety consultant with Fitch & Associates.
"There are a number of factors that can drive it, but generally what it is is the radio channel is just too busy because there are too many people trying to get on a single radio channel at a single point in time," he said.
It's a problem experts on the technology side see often with radio systems that aren't reliable due to age.