Authorities in Windsor say Matthew Coleman, 37, had brought the 9mm handgun into the couple's bedroom for safekeeping out of concern that children in the house might play with it.
The gun went off, and a bullet struck Dorthea in one leg and exited through the other.
Emergency services were called to the scene, and Dorthea was rushed to a nearby hospital. She was conscious and alert at the time.
The county's Deputy State’s Attorney David Cahill said Coleman avoided a harsher charge of aggravated assault because he failed to demonstrate "extreme indifference to human life."
"Simply put, the state has charged Mr. Coleman for making a tragic, easily avoidable mistake," Cahill told reporters.
Coleman pleaded innocent just the same.