A new study from the University of Illinois at Chicago’s School of Public Health finds that police officers are more likely to be killed in states where more people own guns.

“If we’re interested in protecting police officers, we need to look at what’s killing them, and what’s killing them is guns,” says David Swedler, one of the study’s authors.

The study also determined that gun violence constitutes the number two cause of on-the-job death for police officers. Swedler and his team used the FBI’s Uniformed Crime Reporting database to check all homicides of police officers between 1996 and 2010, and also employed a survey called the Behavioral Risk Factor Surveillance System to collect data on gun ownership.

“Alabama, Alaska, Arkansas, Mississippi and Montana were the states with the highest rates of both gun ownership and for law enforcement killings. Connecticut, Massachusetts, New Jersey, New York and Rhode Island had the lowest per capita rate for both. It’s important to calculate the rates by per capita, said Swedler, because large states have more killings and more guns simply because they have more people,” writes NBC News’s Maggie Fox.

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