Police said the dispute began when one car was tailgating another in the Michigan town of Ionia, population 11,400.
Both drivers pulled into the parking lot of a local car wash and stepped out of their vehicles, according to ABC affiliate WZZM-TV. Witnesses said the tailgating driver fired first, and the other driver returned fire.
When ambulances arrived, the men -- Ionia residents James Pullam, 43, and Robert Taylor, 56 -- were given medical care and transported to a local hospital, where they were pronounced dead, Detroit News reported.
Both men fired handguns and had valid licenses to carry concealed weapons, according to authorities, Detroit News said.
In Michigan, anyone over the age of 21 can be issued a concealed carry permit as long as they take a short gun safety class and meet a list of eligibility requirements, which include no felony convictions or mental illness diagnoses.
If Pullam and Taylor didn't have concealed carry permits, they would have been required by law to keep their firearms stored in special cases in the trunks of their cars.
(Hat tip, wheezes on Reddit)