NBC News, in the lack of federal movement on the topic, created a criteria for and started tracking school shootings in the wake of the Sandy Hook massacre. We took that data and built an app around it.
The school shooting tracker is a javascript and d3 app with a two-tier Google Sheet backend used for processing and publishing the shootings that meet NBC News' criteria.
The data was leveraged for this piece I edited and assembled that ran on the 10-year anniversary of Sandy Hook: Again and again: The school shootings since Sandy Hook.