The Mass Shooting Tracker (MST) is a crowd-sourced database of U.S. mass shootings. Below is a plain-English guide to MST’s definition, where its data comes from, what the 2025 numbers look like right now, and best practices for citing and comparing the dataset.
How the Mass Shooting Tracker Defines a “Mass Shooting”
MST defines a mass shooting as a single outburst of violence in which four or more people are shot during a single spree. The project explicitly notes this is not the same thing as “mass murder” and that it may include circumstances such as the gunman’s injury or death, or police shootings around the gunman. See MST’s FAQ and About pages for the precise language and rationale.
2025 Snapshot (Live Data on MST)
The MST Data page for 2025 provides a running tally and simple summary. As of the most recent update on the site, you’ll see:
Project scope
U.S. incidents since 1/1/2013 with four or more people shot, compiled by a volunteer team.
Because MST updates continuously, numbers can change day-to-day. For publication, grab the latest totals directly from the live 2025 data page and include the date/time you accessed them.
What’s in the Dataset and How to Use It
MST’s data pages list incidents by date and location with summary fields (e.g., number shot, links to sourcing). The team emphasizes transparency and provides a one-click option to copy summary stats. You can browse by year, scan the feed of recent incidents on the homepage, and use the FAQ for inclusion criteria and edge cases.
Comparing MST to Other Trackers (and Why Totals Differ)
MST counts people shot (injured or killed) and may include the shooter. Other respected sources use different thresholds. For example, the Gun Violence Archive tallies incidents with four or more victims shot, excluding the shooter, while some government and media collaborations focus on “mass killings,” meaning four or more deaths. These choices drive divergent totals even when describing the same year.
