The specific cause has not been identified. On XXX6, my 2025 Chevrolet Silverado 1500 Custom LT Trail Boss unexpectedly rolled away while parked and unoccupied, striking another parked vehicle. The truck remains at Modern Chevrolet and is available for inspection. GM/ESIS opened a safety and product liability investigation and is arranging inspection/data retrieval. I parked at Walmart in [XXX], shut the truck off, exited, locked it, and walked away. Shortly afterward, I heard a sound resembling the key-fob-left-inside warning. My key fob was in my pocket, so I returned and saw the truck moving with no driver. Another person and I tried to stop it. I entered through the driver’s door and pressed Start/Stop several times, but it would not start while moving. It continued moving and struck another parked vehicle. Vehicle dropped off on XXX and Modern Chevrolet could not reproduce the incident or identify the cause. The service advisor stated it “came out of gear but don’t know why” and escalated it to GM. GM/ESIS plans to retrieve SDM/airbag data, and I requested any Tech II/MDI scan data. No warning lights, messages, or chimes were observed during the incident. I did not see/hear “SHIFT TO PARK,” and I was able to lock the truck with the key fob outside. In a later controlled test, I left the truck in Drive and shut it off. It displayed “SHIFT TO PARK” and sounded a warning chime. Opening the driver’s door also produced a key-fob-left-inside-type alert, which did not occur on