Just before 8:30 a.m. Monday morning, a gunman unleashed fire at the D.C. Navy Yard. NBC News has identified the gunman as Aaron Alexis.
At least 12 people are dead, plus the shooter, and a number of others are injured.
Upon hearing of the mass shooting, Twitter exploded using the #NavyYardShooting to send thoughts and prayers to those affected by the shooting, as well as constant updates on what was happening throughout the day.
Abby Borovitz