The MPD activated its newly built Joint Operations Command Center (JOCC). Although it had not officially opened yet, September 11, 2001, became its first day of operations. While some equipment had been installed, other devices, such as phones, had not and had to be installed on the fly as emergency personnel arrived to respond. Officials from various agencies and departments including the United States Park Police, United States Capitol Police, the FBI, Secret Service, and the FAA's military district arrived to respond. Around that time, they were notified that The Pentagon had been hit as well. Though the Pentagon was located across the river in Arlington County, Virginia, MPD officers still responded to assist with the emergency response. Additionally, MPD officers working in conjunction with U.S. Park Police officers locked down all Federal buildings along the National Mall, including establishing a perimeter around the White House.