More than 700 road rage incidents in the United States last year involved a gun and caused more than 500 people to be killed or wounded, according to a report released on Monday.

Last year, the 728 incidents were up from 610 in 2016, according to analysis by nonprofit Everytown for Gun Safety. It was the highest in the six years that the nonprofit organization has recorded incidents.

Road rage shootings killed or wounded an average of 44 people a month last year, double the pre-pandemic average of 22 people each month in 2019.

And road rage shootings are not slowing down this year, according to Everytown. So far, there have been at least 114 incidents of road rage shootings.

The National Highway Traffic Safety Administration defines road rage as an intentional assault with a motor vehicle or weapon that occurs on the road or that started on the road. It is considered a criminal offense.

Sarah Burd-Sharps, director of research for Everytown, blamed people's easy access to guns. "Driving gets heated in plenty of other countries, but only in the US is someone shot and injured or killed every 17 hours in a road rage incident," Burd-Sharps said. "We've seen a national increase in shootings during the pandemic, and this increase has played out on our streets and highways too."

In a statement, Everytown said it does not "definitively know what is driving this increase in road rage shootings, but the pandemic and its continuing effects have brought all kinds of new stressors into people's lives and exacerbated underlying ones".

Anxiety and uncertainty over the COVID-19, in addition to economic uncertainty and other stresses, are causing a lot of anger on the road, said Ryan Martin, associate dean and psychology professor at the University of Wisconsin-Green Bay.

"We're already stretched to the breaking point, and then someone else's driving becomes the last straw," Alex Korb, a neuroscientist, told The Wall Street Journal last month.