Most likely hydrolocked it from leaky head gasket, especially if it did it when starting first thing after sitting for a good bit.
Water ingestion is also a possibility but I have personally seen 3 do this from headgaskets..All high (130k+) miles

The pic is one that did surprising little damage, unfortunally it just taged the block enough to crack it...bearings and crank were perfect.

Rick

6520433-5.7connrod.JPG (97 downloads)

Blown71X V2.0 under construction 71 Cuda 383 4-SPD (maybe for sale) 2010 Challenger B5 Classic