Methodology
Detailed information about our data collection methods, inclusion criteria, categorization system, and verification processes.
Definition of Mass Shooting
For the purposes of this database, we define a mass shooting incident as one that meets the following criteria:
Inclusion Criteria:
Note on Definitions
There is no universally accepted definition of "mass shooting." Different organizations use varying criteria (number of victims, location types, etc.). Our definition aims to capture incidents of significant public concern while maintaining consistency.
Categorization System
Incidents are categorized using a color-coding system to provide quick visual identification of different types of mass shootings:
Incidents where children (under 18) were among the victims
Incidents where both women and children were among the victims
Incidents classified as hate crimes targeting specific groups
All other mass shooting incidents not fitting above categories
Accessibility Note: Categories use both color and pattern (dashed borders for hate crimes) to ensure accessibility for color-blind users.
Data Collection Process
1. Source Identification
We collect information from multiple reliable sources for each incident:
- • Law enforcement press releases and reports
- • Established news organizations (AP, Reuters, major newspapers)
- • Government databases and official records
- • Court documents and legal filings
2. Verification Process
Each incident must be verified through our multi-step process:
3. Ongoing Updates
Our database is regularly updated as new information becomes available or corrections are identified. Each incident includes a "last verified" date to indicate when the information was most recently reviewed.
Data Fields & Standards
| Field | Description | Format |
|---|---|---|
| id | Unique incident identifier | MS-YYYYMMDD-slug |
| date | Date of incident | YYYY-MM-DD |
| location | Type of location | school, workplace, public space, etc. |
| fatalities | Number of people killed | Integer (excluding shooter) |
| injuries | Number of people injured | Integer |
| hate_crime | Classified as hate crime | Boolean + target group |
Limitations & Caveats
While we strive for completeness and accuracy, users should be aware of the following limitations:
Reporting Delays
Some incidents may not appear immediately due to verification time requirements or delayed official reporting.
Evolving Information
Details about incidents may change as investigations proceed. We update records when reliable new information becomes available.
Definition Variations
Our definition may differ from other organizations, leading to different incident counts and categorizations.
Update Schedule & Change Log
Regular Updates:
- • New incidents: Within 48-72 hours of verification
- • Data review: Monthly comprehensive review
- • Source verification: Quarterly source checks
- • System updates: As needed for improvements
Change Documentation:
- • All changes are logged with timestamps
- • Correction reasons are documented
- • Source updates are tracked
- • Major methodology changes are announced
Last Updated: This methodology was last reviewed on June 1, 2024. Any significant changes to our approach will be documented and announced.