WASHINGTON (AP) — Recalling the shooting rampage that killed 20 first graders as the worst day of his presidency, President Barack Obama pledged to put his “full weight” behind legislation aimed at preventing gun violence.

Obama voiced skepticism about the National Rifle Association’s proposal to put armed guards in schools following the Dec. 14 tragedy at Sandy Hook Elementary School in Newtown, Conn. The president made his comments Saturday in an interview that aired Sunday on NBC’s “Meet the Press.”