The images show what appears to be a slug attacking a worm, with a Flatworm in attendance. The final image shows a chunk taken out of the worm by the slug. Closer inspection of the sequence of images also shows White Slug Mites on the slug and the Flatworm and Globular Springtails on the pavers around the periphery of the scene. Thanks to Marcus Leach for help with this sighting.
Aweb search indicates that the introduced Grey Field Slug is an omnivore and that earthworms are amongst its diet, though it mainly feeds on decaying vegetation