By the time the nation confronted the unthinkable school massacre in Connecticut last December, Mother Jones’ groundbreaking investigation of mass shootings, launched the prior summer, had shown that mass gun violence in America was on the rise. The trend appeared to be no coincidence in light of the proliferation of guns and looser gun laws nationwide. One leading criminologist took issue with our criteria, arguing that mass shootings had not become more common. But now, research from an expert on criminal justice at Texas State University further shows that gun rampages in the United States have escalated.

The research, to be published in a book in July, confirms that: