9:42 a.m. September 11, 2001: Arlington County Police Department Starts Establishing Security around the Pentagon Site

The Arlington County Police Department (ACPD) begins securing the perimeter of the Pentagon Reservation just minutes after the Pentagon attack occurred. [Washington Post, 9/20/2001; Goldberg et al., 2007, pp. 162; Defense Media Network, 9/11/2015] Corporal Barry Foust and Officer Richard Cox of the ACPD witnessed the attack on the Pentagon, at 9:37 a.m. (see 9:37 a.m. September 11, 2001), and immediately called the Arlington County Emergency Communications Center to report what they had seen (see (9:36 a.m.-9:39 a.m.) September 11, 2001). ACPD headquarters then sent a pager message to all members of the department with instructions to report for duty, thereby initiating an immediate response to the incident.
Arlington Police Take Charge of Security – Lieutenant Robert Medairos was the first ACPD command-level official to reach the scene and took command of the department’s response there. [US Department of Health and Human Services, 7/2002, pp. C6-C7 ] While the Defense Protective Service (DPS)—the law enforcement agency that guards the Pentagon—has exclusive jurisdiction within the Pentagon Reservation, the ACPD has jurisdiction around it. [US Department of Health and Human Services, 7/2002, pp. C1 ; Historical Office, Office of the Secretary of Defense, 1/31/2006 ; Defense Media Network, 9/11/2019] Medairos therefore promptly comes to an arrangement with the DPS for the ACPD to secure the perimeter of the Reservation.
Police Close All Roads around the Pentagon – Along with his colleagues Lieutenant Brian Berke and Sergeant James Daly, he assesses the road network conditions and identifies 27 intersections that require immediate police posting. [US Department of Health and Human Services, 7/2002, pp. C7 ; Goldberg et al., 2007, pp. 162] At 9:42 a.m., he orders the closure of all roads surrounding the Pentagon. [Washington Post, 9/20/2001] Berke and Daly take action to keep all traffic except emergency vehicles off the feeder roads to Route 27, just west of the crash site. Police officers close Route 27 to regular traffic and prevent first responders from blocking emergency lanes or parking their vehicles haphazardly. The Pentagon’s parking lot and the field adjacent to it are cordoned off, and guards are posted around the perimeter. [US Department of Health and Human Services, 7/2002, pp. C7 ; Goldberg et al., 2007, pp. 162] Sniper teams are set up to monitor the local highways. ACPD officers monitor traffic around the area and screen pedestrians entering the crash site. Anyone delivering equipment has to be escorted to the Pentagon by police officers. [Middletown Press, 1/29/2002]
Other Police Departments Will Assist the Response – The ACPD has a memorandum of understanding with all the other police departments in the area and it calls these departments to request assistance. [Historical Office, Office of the Secretary of Defense, 1/31/2006 ] Consequently, by 11:00 a.m., over 100 law enforcement officers will have reported to the staging area at the Pentagon. Along with members of the ACPD, officers will have come from Fairfax County Police Department, Alexandria Police Department, Arlington County Sheriff’s Office, Arlington County Park Rangers, and the Immigration and Naturalization Service. Captain Rebecca Hackney will soon take over from Medairos as the commander of the ACPD at the Pentagon. Deputy Chief Stephen Holl, who was at a meeting in Richmond, Virginia, when the Pentagon attack occurred, immediately heads back to Arlington after hearing what happened, and will arrive at the ACPD command post at the Pentagon around midday and take over command of the ACPD from Hackney. [US Department of Health and Human Services, 7/2002, pp. C6-C7, C13 ; Goldberg et al., 2007, pp. 162, 164]