Polyphemus tears a part off a mountain, throws it, and kills Acis.

The Cyclops followed him close, then wrenched a part of the mountain
away from its side, and hurled it at Acis. Although his rival
was only struck by the edge of the rock, it crushed him completely.

Metamorphoses, "Acis, Galatea and Polyphemus," Translated by David Raeburn.