I couldnt believe my eyes when I saw my pygmy cory push off a ramshorn snail from the glass and attack the flailing body of the snail!

Im pretty sure its accidental though

. Only seen this once, but the pygmies came here 2 days before, so u never know. They have not beeen aggressive to the youngest and smallest shrimplets(so far). Tehy spend time swimming next to the glass and hovering in midwater, or resting on java fern and moss. Occasionally they forage arounf on driftwood, moss, leaves and substrate, so this behaviour took me by surprise. If its repeated, I'll try to get pics.
Any explanations would be great!