Are Mass Shootings Becoming More Frequent--and More Deadly?

In the wake of Friday morning's horrific mass shooting at a movie theater in Aurora, Colorado, which left at least 12 dead and 59 wounded, many people around the country have begun to question their safety.

The alleged gunman, James Holmes, 24, reportedly burst into the theater about 30 minutes into the midnight showing of "The Dark Knight Rises," and began walking up and down the aisles, methodically shooting moviegoers as they sat trapped in their seats. His victims never had a chance.

All indications are that Holmes acted alone, and he has been arrested, so the threat posed by this specific offender has been removed.

However, as Americans face the prospect of leaving the security of their homes and going to public malls, schools, restaurants, and movie theaters, they may reasonably wonder about the risks they face. Are they in more danger today than they were in the past? And are these types of attacks getting worse--more frequent and more deadly?

Some answers can be gleaned from the New York Police Department's recent study of "active shooters"--perpetrators who killed or attempted to kill people in a confined and populated area, and who harmed random innocent victims beyond any specific, targeted individual. Its data show that from 1966-2010, there were 179 active shooter incidents in the United States that resulted in at least two casualties.

Overall, the frequency of these incidents in the U.S. rose dramatically, with 18 attacks occurring from 1980-1989, 54 attacks from 1990-1999, and 87 attacks from 2000-2009. Worse yet, over this time span, the number of attacks resulting in at least five fatalities more than tripled, from 6 high-fatality shootings in the 1980s to 19 high-fatality shootings in the 2000s.

Following Holmes' attack on the movie theater in Aurora, four of the ten most lethal mass shootings in U.S. history have now occurred in the past six years. The other three are Nidal Hasan's attack at the Fort Hood Army base in 2009, Jiverly Wong's attack at a Binghamton immigration center in 2009, and Seung-Hui Cho's attack on the Virginia Tech campus in 2007.

The worst of these was the Virginia Tech massacre, which left 32 dead and 20 wounded, not included Cho, who committed suicide. However, if reports of at least 12 dead and 59 wounded in Aurora are accurate, that would mean that Holmes's attack resulted in more total casualties (fatalities plus injuries) than any prior shooting on U.S. soil.

And the Aurora attack comes less than one year after Anders Behring Breivik set the international "record," killing 77 and wounding more than 200 in his combined bombing/shooting attack in Norway.

On a national scale, mass shooters pose a far lesser threat to human survival than many everyday activities, such as driving. Traffic fatalities kill more than 30,000 people per year in the U.S., while on average, mass shooters kill less than 100. However, that will come as little comfort to the victims in Aurora--or their families.

The fact remains that mass shootings are increasingly common and increasingly deadly. And there's no clear end in sight.