Athena realized that Laocoonte had found out about the Trojan Horse plot. Because she sided with Sparta, she sent her enslaved serpent to assault Laocoonte before he could let the secret out. The serpent sank its fangs into the dissident Laocoonte, tearing him to pieces before gulping him down. It then proceeded to destroy the city of Troy.
See Slithering Serpent.