Mass shootings in Atlanta, Georgia, and Boulder, Colorado, have once again brought questions of gun control to the fore.

One possibility with Democrats in power in Washington is a revival of a federal assault weapons ban.

The last federal assault weapons ban expired in 2004, but a new study from Northwestern Medicine says that the ten-year ban likely prevented as many as 11 mass shootings, and had it remained in place, as many as 30 more mass shootings could have been prevented.

The lead author of the study is Lori Ann Post, professor of emergency medicine and medical sciences at Northwestern University’s Feinberg School of Medicine.

Post says that what makes her study unique is that it focuses just on mass shootings whereas previous studies into the effectiveness of the assault weapons ban had looked at overall gun deaths.

“The big thing about my study that is really different from every other study is I find that if you prevent the access to assault weapons, high capacity magazines, and semi-automatic or rapid-fire guns, it prevents the actual incident itself. All of the other studies have looked at how to reduce the lethality of these events,” said Post. “But I find that people don’t even go out and do a mass shooting in the absence of an assault rifle.”

Post says that her numbers are based on analyzing the trend of mass shootings before the implementation of the assault weapons ban in 1994, what happened during the ban, and then what happen when it expired in 2004.

Although deaths in mass shootings account for less than 1% of all gun deaths in the United States, Post says she wanted to focus on the issue of mass shootings because of the impact that they have on the American psyche.

“They are such high media events. Every time there is a mass shooting – even though they account for less than 1% of all gun deaths each year – this is what gets people riled up and this is when people start talking about gun policy,” said Post.

Post herself is a member of the National Rifle Association and says most of the NRA members she knows are in favor of commonsense gun control measures.

“I think that we have to start someplace, and I think it’s the one thing that pretty much both sides of the aisle can agree to, when you shoot a roomful of people, or a school or a movie theater or a grocery store or a shopping mall, it is a tragic event and it makes everybody feel very bad,” said Post. “And I think it is a commonsense law to prevent access to rapid-fire assault weapons which are military grade and large capacity magazines that mean you can shoot a hundred rounds per minute.”

But Richard Pearson, executive director of the Illinois State Rifle Association has doubts about Post’s data, saying that it was “just supposition,” and that neither he nor his organization would back an assault weapons ban.

“I’m certainly not going to support it and the Illinois State Rifle Association is not going to support it because you are talking about the most popular sporting rifles in the United States,” said Pearson. “So we’re not going to buy into that program.”

Pearson said taking away guns from legal owners would not stop the epidemic of gun violence because, especially in Chicago, many of the guns used in crimes are obtained illegally.

He also notes that often laws that are on the books are not enforced.

“The latest guy who shot up a store in Boulder. The laws were in place to take care of him yet they didn’t do anything about it again,” said Pearson.

But Post says that properly implemented background checks can be effective and help identify people with a likely propensity toward gun violence. Mass shooters “are not mentally ill, they are evil,” says Post. “And there are ways that you can identify anti-social personality disorders over time.”

Post says studies have shown that media coverage of mass shootings can also spur other would-be shooters to action.

“Those types of people, we know what drives them,” said Post. “We know that they like notoriety. They want to make it into newspapers and see themselves on television.”

She said that after the high-profile coverage of the spa shootings in Atlanta, she expected another mass shooting to follow and so was not surprised by what happened in Boulder.

“What usually happens is that all that media coverage then expedites the next shooting because people see all the media attention and say ‘I want to do (my mass shooting) now too,’” said Post. “So I assumed another one would follow immediately and it did.”