The Preventable Mass Shootings Database is a work in progress and it always will be.

We conduct exhaustive ongoing research. As new data is discovered and/or released we review and edit as necessary our findings. We also adjust our findings based on legitimate external feedback that is received questioning the validity of incident content. Finally, and to a much lesser extent, we edit our findings due to the contemplated product of authors and editors which inevitably happens. Therefore, the Preventable Rankings Score and resulting Preventable Status which has been assigned to each incident are sometimes in a state of flux, particularly with the most recent incidents, because the passage of time tends to result in the dust settling. However, even with older incidents, there still remains a possibility that new data will develop.
Preventable Rankings Score:

⯆ = Trending Down – May Decrease.
⯅ = Trending Up – May Increase.
⯀ = Closed/Stagnant – Unlikely to Change.