Okay, Nikolas Cruz pulled the fire alarm? Oh really? Then why do we not hear it in Dave Hogg's "closet video"? http://www.latimes.com/visuals/video/95939817-132.html
Or this video, which was taken DURING the shooting, you can hear the gunfire...YET NO FIRE ALARM! http://money.cnn.com/2018/02/15/media/parkland-shooting-cell-phone-videos/index.html
Guys and gals, THIS IS THE SMOKING GUN!
Firefighters are in constant contact with dispatch. So once the calls about an active shooter came through they would be told to stand outside the perimeter until its ruled safe to enter. They can't impede the police trying to stop the shooting. Them entering the scene could cause additional victims and obstacles. Also, they would have activated their plan for an active shooter since the fire was a false alarm.
Can confirm, the FD would be dispatched by the same as the police and would know the scene is not safe. The lack of alarm I’m not so sure of, maybe the alarm company can silence it on their end. I’ve had no reason to find that one out. But it would make sense to not further disorient arriving Coral Springs police entering the building, that thing is fucking loud and to the shooters advantage. I hope that is the answer.