2014 GMC Sierra 6.2 ecotec All Terrain 102k miles. Yesterday morning I was driving to work cruising about 45 miles per hour and the truck lost power. Heard a "chirp" noise and truck died while driving Headlights cut off, engine off, no power steering, just coasted into a CVS parking lot and parked it. The battery was dead and couldn't turn the engine over (battery is 3 months old and never had an issue). I came back about an hour later and jumped the truck and it started but was running rough and making a sound I can only describe as a squeak with a slight knocking sound. Oil pressure was steady at 40 psi and no check engine light.I had it towed to a mechanic and his preliminary diagnosis was a spun rod bearing. I've never had any engine problems with this truck, always used synthetic 0w20 oil and never went over on an oil change. The engine has a perfect idle and prior to this ran great with no issues. I had a tune done around 40k miles ago and had the DOD disabled so it only ran in V8 mode. I was just rear ended the night before and other than cosmetic damage to the rest bumper the only viable damage was to my exhaust. It was hit when the car rear ended me and was pushed forward. I don't see how a rear end impact could be connected. But I also don't know how a spun rod bearing could kill the battery. I'm confused and didn't know if this was something anyone else has experienced.