There is no way to list or train for the innumerable mass casualty scenarios that a responder could face on any day, at any time, in any place. This means that no emergency response can be perfect and no plan flawless. However, rather than focusing on the “what ifs” after an incident, responders need to decide on the “what nows.” The military and civilian responders to the 16 September 2013 Washington Navy Yard shooting have done that. Not only have the involved agencies created their own lessons learned, they have also coordinated with each other to bridge the response gaps that were exposed. Key takeaways from the shooting as well as actions that have been taken since the incident were shared on 17 September 2019, when public safety agencies throughout the National Capital Region convened to reinforce communications efforts and address any remaining interoperability concerns.