Manual Transmission problems of the 2003 Mazda B3000

My 2003 Mazda B3000 pickup spontaneously shifted from neutral into reverse and crashed the (driver's side) open door into the inside wall of my garage. The vehicle was idling and unoccupied, and the parking brake was not engaged. The force of the crash was enough to bend the door. I called the local police department, but was informed that they do not issue report numbers for minor losses incurred on private property. I am filing this report in view of the potential for serious bodily harm, death, or major property damage associated with a spontaneous shifting from neutral into a gear, so that the vehicle travels without any occupants, and poses the risk of crashing.