Many times with false flag terrorist attacks, there will be coinciding drills; this is so that the conspirators can gain full spectrum dominance at the scene, and also exercise the benefit of plausible deniability should their ground zero presence lead to any suspicions that they may be involved.

Another benefit for having a drill to coincide with a terrorist attack is to stop would-be heroes from hindering the impact of the attack by killing the terrorist (or patsy) prematurely. [1]
Learn more about staged-drills + terror attacks.
VIDEO: YouTube.com/user/AssociatedPress
"I assume that it's a code red drill, because they told us earlier in the day that we were going to be having a code red drill. I assumed it was blanks." – Ernest Rospierski
What we have here, yet again, is another terrorist attack which appears to coincide with a drill that may have been scheduled to happen on the exact same day that the school shooting occurred. As you can see, it put this teacher in a state of temporary disbelief.
Had he been armed, he may have killed the terrorist. However, he also may not have, because the presence of the code red drill could potentially have psyched him out just long enough to cause hesitation.
Click the image below to watch Terrorstorm in full.

IMAGE: DVD Cover Art for Terrorstorm
[1] Q: If Nikolas Cruz was a patsy, how could he be manipulated into bringing guns to school?
A: Research scopolamine, hyoscine, devils breath, or burundanga. Scopolamine can rob you of your will, and make you compliant to the verbal commands of others.
- Student: Connor Dietrich thought it was a drill.
- Student: Kelsey Friend thought it was a code red drill.
- Teacher: Melissa Falkowski thought it was an Active Shooter Drill
- Second Student Witness Says Up To Three Shooters In Parkland Florida School Mass Shooting
- Multiple Shooters Participated In Florida School Shooting According To Eyewitness Alexa Miednik