As Memphis Police Department squad cars cruise parking lots and streets, their license plate readers scan nearby vehicles and analyze the associated records, looking for outstanding warrants. Officer Matt Cunningham, left, and John Harvey, the Memphis Real Time Crime Center systems manager, check a record that popped up as an alert in the system. (Photo by Michael S. Williamson / The Washington Post)
From the top floor of the William R. Snodgrass Tennessee Tower in Nashville, the Tennessee Office of Homeland Security monitors terrorism threats to the state. It's just one of many agencies working on counterterrorism in Tennessee. (Photo by Michael S. Williamson / The Washington Post)
The Tennessee Office of Homeland Security, housed on the top floor of a Nashville tower, was created in response to the Sept. 11, 2001, attacks. (Photo by Michael S. Williamson / The Washington Post)
Representatives of various agencies - including police and fire departments, the National Guard, the Tennessee Bureau of Investigation and the FBI - attend a threat briefing at the National Guard Armory in Nashville. (Photo by Michael S. Williamson / The Washington Post)
A secure meeting at the National Guard Armory in Nashville is closed to outsiders. The federal government has given security clearances to some state and local officials so they can discuss classified threat information. (Photo by Michael S. Williamson / The Washington Post)
The site in Murfreesboro, Tenn., where local Muslims want to build a new Islamic center. After a recent court battle over the construction, a judge ruled it could continue. (Photo by Michael S. Williamson / The Washington Post)
The FBI is investigating vandalism and arson in at the site in Murfreesboro, Tenn., where local Muslims want to build a mosque, community center and school. (Photo by Michael S. Williamson / The Washington Post)
A poster asks for information about an arson incident in Murfreesboro, Tenn. Many in town see the vandalism as an attempt to intimidate Muslims and stop them from building a new Islamic center. (Photo by Michael S. Williamson / The Washington Post)
The town square in Murfreesboro, Tenn., where some residents have tried to stop the construction of a new Islamic center. (Photo by Michael S. Williamson / The Washington Post)
The headquarters of the Tennessee National Guard's 45th Weapons of Mass Destruction Civil Support Team is in Smyrna. While it was created after 9/11 to respond to terrorism threats and acts, the team mainly does support work for athletic events, NASCAR races and training. (Photo by Michael S. Williamson / The Washington Post)
In the garage of the 45th Weapons of Mass Destruction Civil Support Team, unit members go through biohazard suit training. From left, Sgt. Jason Barfield (yellow suit), Sgt. Mike McIntyre, Sgt. David Owen and Sgt. Tony Dooley. (Photo by Michael S. Williamson / The Washington Post)
The 45th Weapons of Mass Destruction Civil Support Team is one of at least 50 such units created to respond to a chemical, biological or radiological attack. From left, Sgt. Mike McIntyre, Sgt. David Owen and Sgt. Jason Barfield go through biohazard-suit training at the team's garage in Smyrna, Tenn. (Photo by Michael S. Williamson / The Washington Post)
Sgt. Jason Barfield of the 45th Weapons of Mass Destruction Civil Support Team learns to use a camera while wearing heavy gloves. (Photo by Michael S. Williamson / The Washington Post)
In Memphis, police license plate readers scan nearby vehicles with military-grade infrared cameras. (Photo by Michael S. Williamson / The Washington Post)
A Memphis police officer approaches a house to serve a warrant. As part of the department's data-collection efforts, its technology specialist persuaded the local utility company to give the police a daily update of customers' names and addresses. (Photo by Michael S. Williamson / The Washington Post)
The Department of Homeland Security helped the Memphis police buy 90 surveillance cameras, such as this one mounted on a pole in a high-crime neighborhood. (Photo by Michael S. Williamson / The Washington Post)
The Memphis Police Department uses helicopters equipped with military-style infrared cameras to help officers on the ground. Piloting this chopper are Lt. Mark Rewalt, left, and Sgt. Gary Curry. (Photo by Michael S. Williamson / The Washington Post)
From the sky, Lt. Mark Rewalt keeps an eye on a Memphis bridge. The Department of Homeland Security has helped the Memphis police buy equipment to monitor area bridges. (Photo by Michael S. Williamson / The Washington Post)
A large mall during the holiday shopping season is a prime target for auto break-ins, so the Memphis police has stationed mobile surveillance cameras in many mall parking lots. The cameras send video to the department's Real Time Crime Center. (Photo by Michael S. Williamson / The Washington Post)
A Memphis police helicopter's searchlight illuminates a traffic circle. (Photo by Michael S. Williamson / The Washington Post)
A mobile surveillance camera monitors a parking lot in Memphis. (Photo by Michael S. Williamson / The Washington Post)
At the Memphis Police Department's Real Time Crime Center, officer Brian Shivley watches one of the many video feeds from cameras placed throughout the city. (Photo by Michael S. Williamson / The Washington Post)
At the Real Time Crime Center, the surveillance cameras' zoom capability lets officers get a close look at what's happening on Memphis's streets. (Photo by Michael S. Williamson / The Washington Post)
Secure entrances to the Memphis Real Time Crime Center feature fingerprint scanners. (Photo by Michael S. Williamson / The Washington Post)
The FBI data center in Clarksburg, W.Va., houses the National Instant Criminal Background Check System. A board keeps a count of the millions of checks it performs. (Photo by Michael S. Williamson / The Washington Post)
These backup tapes in the FBI's computer center in Clarksburg, W.Va., are part of a system that can perform 8 million background checks per day. (Photo by Michael S. Williamson / The Washington Post)
At its data center in Clarksburg, W.Va., the FBI stores 96 million sets of fingerprints from people across the country and from prisoners in Afghanistan, Iraq, Saudi Arabia and Yemen. State and local officials help supply the domestic records. (Photo by Michael S. Williamson / The Washington Post)
A sign on I-270 urges motorists to "Report Suspicious Activity." The phone number connects callers to the Maryland Coordination and Analysis Center. (Photo by Michael S. Williamson / The Washington Post)
Another sign, this one in the District at 16th Street NW at Harvard Street, is part of a nationwide campaign to remind Americans to be vigilant. (Photo by Michael S. Williamson / The Washington Post)