WATCH: Broward County Sheriff Scott Israel said police continue to receive false reports and "copycat threats" following the deadly shooting at a Florida high school, calling the perpetrators "pathetic".

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AR-15-style semi-automatic rifles have become commonplace in some of the United States’ deadliest mass shootings.

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In addition to this week’s shooting at a Florida high school that left 17 people dead, the shooters in attacks that took place in Newtown, Conn., in 2012, San Bernardino, Calif., in 2015, Orlando, Fla., in 2016, Las Vegas, 2017, and Sutherland Springs, Texas, 2017 all used AR-15 (or AR-15-style) semi-automatic rifles.

Questions have been raised about the consistent use of the AR-15 in U.S. mass shootings since it came out that the shooter who opened fire on Marjory Stoneman Douglas high school in Parkland, Fla., Wednesday used one to carry out the attack.

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Law enforcement said the suspect had legally purchased his AR-15 rifle about a year ago and had posted images of himself on social media holding the gun. Federal law allows people 18 and over to legally purchase long guns. At 21, people can legally buy handguns from a licensed dealer.

This photo posted on the Instagram account of Nikolas Cruz shows weapons lying on a bed. (Instagram via AP) This photo posted on the Instagram account of Nikolas Cruz shows weapons lying on a bed. (Instagram via AP) This photo posted on the Instagram account of Nikolas Cruz shows weapons lying on a bed. (Instagram via AP) This photo posted on the Instagram account of Nikolas Cruz shows weapons lying on a bed. (Instagram via AP)

Andrew Somerset, an expert on American gun culture, explains that the AR-15’s popularity with violent criminals has to do with the amount of damage the weapon is capable of doing, coupled with the continued media focus on the weapons used in these shootings.

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“What the mass shooter is looking for — because they want to cause mass casualties — is a rifle that has a large magazine capacity, interchangeable magazines so they can easily change magazines and shoot a large quantity of ammunition, quickly, and kill a lot of people,” said Somerset, whose book Arms, the Culture and Credo of the Gun, came out in 2015.

AR-15 (or ArmaLite 15) rifles are technically designed for sporting use, as they are not fully automatic assault weapons. However, a semi-automatic action is designed for a series of fast, aimed shots on a battlefield. While the magazines are designed to hold 30 rounds, they can be legally reduced through magazine limits. Florida has not implemented any such restrictions.

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“So the AR-15 and other similar rifles fit the bill,” Somerset added.

The National Rifle Association (NRA) has called the AR-15 the “most popular rifle in America,” touting its customizable features and ideal use for sport shooting, hunting and self-defence situations.

In addition, Somerset said that those inclined to commit these kinds of crimes are often influenced by the actions taken by individuals who’ve committed similar crimes.

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“The profile of your mass shooter is fairly well known and reasonably consistent …There is a copycat element going on,” said Somerset.

He added that the military appearance of the AR-15 has a lot to do with its prevalence in mass shootings.

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“At this point in history, when the United States has been going through its war on terror and so on, and sort of the special forces have been elevated to a place in the American imagination, people want that cache, and your mass shooter is looking for that look-cool factor. They want the cool-looking rifle, the tactical vest and so-on.”

Jooyoung Lee, a professor with the department of psychology at the University of Toronto, says the marketing around the AR-15 could also contribute to its recurrence in these incidents.

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“The AR-15, because of its frequent use in mass shootings and because of its clever marketing by the various firearm manufacturers that make models that are similar to the AR-15, has become a sexy gun — a gun that young men, in particular, want to own because it makes them feel strong.”

He added that mass shooters have a tendency to idolize previous killers, which could lead to similarities in the nuances of the crimes.

John DeCarlo, a criminal justice professor at the University of New Haven and former police chief, agrees with this assessment.

“These have become popular in the public consciousness and the type of individuals committing crimes like this would be very focused on crimes that have preceded their own.”

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DeCarlo also stated that the problem of “glamourized” guns in American culture goes beyond the AR-15.

“A gun is more than a gun here. It’s fetishized. It’s a lifestyle,” said DeCarlo.

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