When President Barack Obama stepped into the White House press room to talk about the latest mass shooting, this time in Oregon, he said with visible regret that such tragedies have become routine.

What we’ve seen at PolitiFact is that with each such event, the claims and counterclaims fly from both sides in the gun debate. It can be difficult to sort fact from fiction.

Politicians and pundits deploy statistics from two basic starting points. Some focus on the number of gun deaths to build the case for a more robust government response.

Other claims focus on gun laws. Opponents of gun restrictions muster stats to say stricter laws have no effect, while advocates offer numbers to prove the opposite.

Here’s how the rhetorical battle played out recently.

Guns as a public health threat

In his White House comments, Obama urged the media to compare the death toll from gun violence to the number of terrorism victims.

A New York-based group called NowThis took him up on his challenge. Boiling the numbers down into a single image spread on social media, its message said 24 Americans have been killed by terrorism in the last decade, while 280,024 Americans were killed by guns.

While those numbers aren’t perfect, the overarching point is accurate. Our review found 71 deaths from jihadist and non-jihadist terrorism on American soil. For gun deaths, the viral image counts homicides and suicides. Suicides account for about 60 percent of all fatal gun violence. If you include them, we found some estimates push the total to over 300,000 since 2005. That means there have been more than 4,000 times as many deaths from guns as from terrorism. We rated the claim Mostly True .

New York Times columnist Nicholas Kristof offered a comparison guaranteed to raise eyebrows. Kristof wrote in an op-ed that each year, the death toll from guns is higher for preschoolers than it is for on-duty law enforcement officers. We went to the FBI and Centers for Disease Control and Prevention statistics and pulled the numbers back to 2008.

Kristof relied on the U.S. Education Department definition of preschoolers and counted kids from birth to 4 years old. We looked at that and also used the CDC’s more limited age group of 3 to 5 years old. In both cases, we included accidents and homicides.

For Kristof’s preferred age group, his claim held up in every year back to 2008. Using the CDC age range, he was correct in four out of the six years. Based on the raw numbers, we rated this Mostly True .

Kristof has a knack for provocative comparisons. About a month before the Oregon slayings, he wrote that "more Americans have died from guns in the United States since 1968 than on battlefields of all the wars in American history."

That rates a full True on the Truth-O-Meter. Yes, about 750,000 Americans died in the Civil War and another 400,000 in WWII, and nearly 60,000 in Vietnam, plus you have every other conflict from the Revolution to Iraq and Afghanistan. The rough total is about 1.4 million.

Since 1968, guns have killed about 1.5 million people.

Do guns laws help?

At his White House press conference, Obama also said that "states with the most gun laws tend to have the fewest gun deaths."

That statement rests on a 2015 National Journal investigation , which considered seven types of gun control from handgun registries, to open carry permits, to gun purchase waiting periods. It found that states that had more restrictive laws within these categories generally had fewer annual gun deaths. An American Medical Association study reached the same conclusion.

But Garen Wintemute, director of the University of California-Davis Violence Prevention Research Program, pointed out that the correlation between restrictive laws and fewer deaths "essentially disappeared" when firearm ownership rates were taken into account.

"Perhaps these laws decrease mortality by decreasing firearm ownership, in which case firearm ownership mediates the association," Wintemute wrote. "But perhaps, and more plausibly, these laws are more readily enacted in states where the prevalence of firearm ownership is low — there will be less opposition to them — and firearm ownership confounds the association."

The catch is, cause and effect are tough to prove. On top of gun ownership, the rural/urban population split and demographics seem to matter. Also, in states with more gun control laws, it looks as though fewer suicides account for most of the reduction in gun deaths.

But the correlation that Obama described is there. We rated his statement Mostly True .

On the flipside of the gun debate, Fox News host Eric Bolling was adamant that not only do gun laws not help, he asserted that nations with the strictest laws have more gun violence.

There’s no data to back that up. Among America’s industrialized peers, every nation that reports its data to the United Nations has tougher gun rules and much lower rates of firearm homicides. (Russia is the most notable exception that does not report data.) According to the latest government data, the United States has a gun homicide rate nearly six times greater than Canada, which has the second-highest rate among the wealthy nations. We rated this claim False .

MSNBC’s Joe Scarborough raised a sobering point for those who back universal background checks. Scarborough himself supports that policy but he said only about 3 percent of crimes are committed with legally purchased guns. Essentially, guns and crime are linked in a way that a popular gun control measure would not touch. But that’s a tough case to prove.

There isn’t research that looks at the total universe of violent crimes and connects them to the source of guns. As it turns out, guns are recovered in a relative handful of crimes.

Some studies have worked the question from the opposite direction. Researchers asked convicted criminals where they got their weapons. A study of prisoners in Chicago’s county jail found that about 3 percent bought their guns at a gun store. The rest got them from family or friends, or on the black market.

That’s not a perfect answer either, though. It’s possible to lie and make an illegal purchase at a gun store, and in some states, it’s legal to get a gun from a family member. So knowing the source doesn’t always tell you whether the criminal got a gun illegally.

Nationally, in a survey of prison inmates, about 40 percent said flat out they got their weapons on the black market. Because of the lack of hard evidence, we rated Scarborough’s claim Half True .

Nevertheless, national universal background checks remain popular. When a gun control advocate tweeted that 90 percent of the public backs that idea, our PolitiFact Texas colleagues found that surveys back that up. In the most recent poll, 93 percent backed universal background checks. Earlier surveys this year found support in the mid to upper 80 percent range. We rated the claim True .

There is an old claim in circulation that holds that 40 percent of guns are sold without background checks. Mark Kelly, the husband of former congresswoman Gabby Giffords, herself a shooting victim, made that point on cable news. The problem is, this claim is based on a small study done two decades ago at a time when gun laws were different. Even the authors say they’re not sure if it still holds true today. We rated it Half True .

Read our supplemental report, "Experts: Values can trump data in gun debate."