Well, she never taught him lesson #1-never point a gun at a person.
She didn't bother to lock her gun and store the ammo separately (That's a big deal in my state during vehicular transport!)
She didn't bother to keep her gun out of the reach of her son.
And, she ensured that her negligence left her son motherless.
I wonder if she put her kid in a safety seat if he was able to find the gun under the seat. If he was buckled in, then he wouldn't have been able to reach under the seat.
Yeah, she made a lot of bad choices and, unfortunately, paid some pretty serious consequences for them.