Officials say they saw a vehicle driving erratically and began to follow the car and attempted to pull it over.
The driver got out and ran from the scene but the passenger, 50-year-old Tonya Johnson, climbed over the center console and sat in the driver's seat.
Officers searched the vehicle and found a black purse that contained a .40 caliber firearm with ten rounds of live ammunition.
Johnson was arrested and booked into the Fresno County Jail for various weapons offenses.