The San Bernardino shooting continues a disturbing trend: No week since 2013 without a mass shooting

This story originally ran in October, after the shooting in Oregon. The graphic has been updated in light of the December 2 shooting in San Bernadino.

Shortly after news broke of a shooting in Oregon on Thursday, my phone rang. It was Donald Trump, who does not normally call.

He wasn't calling about the shooting but had obviously heard of it. "Absolutely a terrible tragedy," he said. "It sounds like another mental health problem. So many of these people, they're coming out of the woodwork. We have to really get to the bottom of it. It's so hard to even talk about these things, because you see them and it's such a tragedy. It's happening more and more. I just don't remember — years back, I just don't remember these things happening. Certainly not with this kind of frequency."

Trump's perception is probably widely shared. A variety of factors make it hard to compare current shooting regularity with the past, including disputed definitions of what constitutes a "mass shooting," the amount of media attention shootings get and the lack of comprehensive data from said past. But we can say with specificity that mass shootings are not uncommon.

In fact, using data from ShootingTracker.com, we can say that mass shootings — defined as incidents in which four or more people are shot — have happened hundreds of times over the last several years. In fact, during President Obama's second term, a Sunday-to-Saturday calendar week has not passed without a mass shooting incident.

Only once have seven days passed without a mass shooting and only once have eight days passed. Those are the longest spans — the latter happening in April of this year. Several times, six days have passed.

The most people shot in one day was on May 12, 2013, with separate mass shootings in Arizona, New Jersey, California and Louisiana.

Again, it's impossible to tell if Trump's assessment of the frequency of shootings is correct. But one thing is indisputable: They are frequent.

Speaking at the White House on Thursday, a visibly frustrated and emotional President Obama remarked on the deadly shooting at a community college in Oregon. (Video: AP)