The Sandy Hook Elementary School shooting occurred in Newtown, Connecticut, within Murphy's House district near the end of his term. In the aftermath of the shooting, he became a leading voice in the movement to prevent gun violence, supporting numerous policies including universal background checks and ending the ban on gun violence research at the CDC. Murphy supported the bipartisan Manchin-Toomey background checks proposal, which would have strengthened and expanded the existing background check system and established a National Commission on Mass Violence to study in-depth all the causes of mass violence.