u/Background_Milk9119

My mother was driving in her Honda Civic Si 2006, and was backing up, and the car stalled while reversing. Then she was suddenly struck in the back of the head and in her stomach by a loud bang, followed by a strong Gunpowder smell and her ears ringing.

I checked the car to see if any of the airbags went off, none did.
And the Gunpowder smell dissipated but still remains in the middle of her seat.

We have no clue what happened, I looked around but nothing was out of the ordinary.
I know very little about cars, so I was hoping to find an explanation here.