Witnesses say distraught family members were yelling the gun just went off as deputies rushed in and tried to revive the woman right there on highway.
It happened on Highway 175 just north of Miller Park.

One of the first witnesses tell us it was absolute chaos when he got to the scene, as people driving by worked quickly to get the car out of traffic all while trying to save the woman's life. 

"They said someone had been shot. She had been shot. I heard several times, "the gun went off, the gun went off!" said Troney Shumpert, who was one of the first people on the scene. 

He was driving to work on when he saw a woman screaming for help and this car stalled.

"From there I noticed the individual, the female in the front of the car and from there, it was a really chaotic scene," he said. 

The Milwaukee County Sheriff's Office says around 10:30 Tuesday morning, the woman driving this car on US 175 north of Miller Park when she was shot in the back.

"I told people not to move her not knowing where the bullet had entered," he said. 

The sheriffs office says a child in the back seat of the car got a hold of a gun, firing a single bullet at the 26-year-old woman. The witness tells us he saw two very young children in the backseat. 

"Two kids, might have ranged from two years old to maybe four or five," said Shumpert. 

Parent and gun store owner Jake Schneider says even a safety device wouldn't have prevented this tragedy.

"You need to always have control of your firearm; it needs to be on your person and in a holster to so its being carried safely," said Schneider. 

He says parents who own guns need to do more than tell their children to stay away from the gun. 

"If they are old enough to be even taught firearm safety they should because you'll remove the mystery or mystique of the firearm. You take that
away and train them how to use it and respect it," he said. 

And in this case it ended tragically. Despite lifesaving efforts the driver who was shot died at the scene. 

It's still not clear where the gun was in the car, or how the people involved were related. 

Meanwhile Schneider says, if you think your child is too young to learn about firearms, more the reason to always keep them in your possession.