The mayors of New York and Boston are speaking out on behalf of an anti-gun violence group.

Mayor Michael Bloomberg and Mayor Thomas Menino are co-chairs of Mayors Against Illegal Guns.

Menino said he is overcome with both grief and outrage following the mass shootings of 20 children and six adults at the Sandy Hook Elementary School in Newtown, Connecticut. The shooter also killed his mother and took his own life, bringing the total death toll to 28.

Menino said a national policy on guns should get rid of loopholes in gun laws and get automatic weapons out of neighborhoods.

Bloomberg noted that critics said it was "too soon to talk about gun laws" after other high-profile shootings.

He said the White House and Congress have not shown leadership on the issue.