I was trying to think of all the issues I have heard about with Parkland.
1. The officers did not enter the building immediately or even minutes later when more officers were available.
1A. This was not just on the one officer, but that decision was backed up by others once more people showed up who were also prevented from immediately entering.
2. The killer was a known felon that was never actually tagged with a felony even though he should have been.
3. As mentioned, the security cameras were on a 20 minute delay that apparently very few people knew about.
I am sure there are more, but I am drawing a blank.