An analysis by vox.com suggests that weaker gun laws and higher rates of gun ownership do, at the very least, correlate with more killings by police officers (including shootings and other incidents of lethal force). The theory is that behind virtually all police shootings is a constant fear that a gun may be present.

The police have good reason to be fearful. The US has a tremendous amount of civilian-owned guns — far more than any other country in the world. Based on recent estimates, there are more firearms in America than there are people. That presents a constant potential threat to police.

“Police officers in the United States in reality need to be conscious of and are trained to be conscious of the fact that literally every single person they come in contact with may be carrying a concealed firearm,” David Kennedy, a criminologist at John Jay College, told me. “That’s true for a 911 call. It’s true for a barking dog call. It’s true for a domestic violence incident. It’s true for a traffic stop. It’s true for everything.”