A locked surveillance room, internal emergency call systems and a complex building layout led to initial confusion regarding the number and identity of perpetrators in the September 2013 Navy Yard shooting in Washington D.C.

It used to be that the word “lockdown” was only used in reference to an emergency protocol to restrict movement in a prison environment.

Forty-eight percent of Americans blame the mental health system “a great deal” for mass shootings in the U.S., unchanged from January 2011, according to a new Gallup poll.

The deadly shooting at Washington D.C.’s Navy Yard is promoting Senators to consider a fresh attempt to advance legislation strengthening background checks for gun buyers, Bloomberg reports.

One suspect is dead after a shooting at the Washington D.C. Navy Yard, according to CNN. Conflicting reports have emerged about whether the suspect worked alone, but multiple people were killed in the Monday morning shooting.