Authorities say at least 26 people, including 20 children, were killed Friday when a gunman opened fire inside a Connecticut elementary school.

READ MORE: As many as 27 killed, many of them children in Connecticut school shooting

After the news broke, Twitter erupted with people expressing their shock and sadness over this horrible tragedy, with #PrayForNewtown, #Newtown and #CTshooting among the top trending topics on the social network.