But criminologists, police, and others have posited several plausible drivers of the current spike. One, most obviously, is the coronavirus pandemic, which affected Americans in many ways. More people were at home, creating different social patterns. More people lost jobs, and might have turned to dangerous and criminal behavior to make ends meet. People were stressed and unhappy. Many public programs that helped divert crime were curtailed or eliminated to prevent the spread of the virus, including violence-interruption programs that have been shown to be effective in reducing gun crime. Without those programs in place, violence built on itself. “We have a vicious cycle. Guns on the street are fueling shootings, and more shootings are fueling more guns on the street,” Jerry Ratcliffe, a criminal-justice professor at Temple University, told me in June.

A second major potential factor is the murder of George Floyd by police in Minneapolis in May 2020, a few months into the pandemic. Floyd’s death—along with several other high-profile killings of Black people by police—set off some of the largest protests in American history, and police came under scrutiny around the country. Although murders were rising before those protests, the largest spike occurred after them (though murders do typically rise in the summer). Murder rates have spiked after previous major protests against police too.

Identifying a factor is not the same as identifying a mechanism, though, and many possibilities exist. Were police absorbed with responding to unrest, creating opportunities for murders away from view? Did police respond to the protests by pulling back from policing, and if they did, was that “blue flu”—the name given for informal work stoppages—or an attempt to respond to communities demanding less policing?