CIA Shooting

A gunman fires on cars waiting near the entrance of the CIA's headquarters in Langley, Va., killing three agency employees and wounding two more. The shooter, Mir Aimal Kasi, was angry with U.S. policy in the Middle East.

photo: Newscom/Dennis Brack

First World Trade Center Bombing

A car bomb goes off below the North Tower of the World Trade Center in New York, where some federal offices are located. The al Qaeda attack fails to bring down the towers as originally planned, but kills six and injures more than 1,000.

photo: AP/Alex Brandon

Oklahoma City Bombing

A homemade bomb destroys Oklahoma City's Alfred P. Murrah Federal Building, injuring more than 800 and killing 168. Army veterans Timothy McVeigh (above) and Terry Nichols were behind the attack. They claimed they acted to protect the Constitution.

photo: AP/David Longstreath

Capitol Shooting

A paranoid schizophrenic enters the Capitol Building and opens fire, killing two police officers.

photo: AP/Khue Bui

African Embassy Bombings

Trucks loaded with explosives go off almost simultaneously outside U.S. embassies in Dar es Salaam, Tanzania (shown above), and Nairobi, Kenya, killing 233. A group linked to Egyptian Islamic Jihad took credit for the bombings, making Osama bin Laden and Ayman al-Zawahiri household names.

photo: AP/Brennan Linsley

USS Cole Attack

An al Qaeda suicide attack damages the Navy destroyer USS Cole in the port of Aden, Yemen, killing 17 sailors and injuring 39 others.

photo: AP/U.S. Navy

Attacks on the World Trade Center and Pentagon

Hijackers linked to al Qaeda crash commercial jets into the World Trade Center and west side of the Pentagon. They hijack a third plane, but passengers seize control and crash the plane, thought to have been headed for the Capitol or White House, into a field in Shanksville, Pa. 189 die in the Pentagon; 2,751 die in New York, and 40 die in Pennsylvania.

photo: AP/Heesoon Yim

Anthrax Attacks

Envelopes containing anthrax and notes with radical Islamist rhetoric are sent to news organizations and two senators. Five people die and at least 22 people—including postal workers—are infected. The FBI said Bruce Ivins, an Army biodefense expert who committed suicide in 2008, orchestrated the attacks himself.

photo: AP/Name

Military Recruiting Office Shooting

A gunman opens fire on a U.S. military recruiting office in Little Rock, Ark., killing one soldier and wounding another. Suspect Abdulhakim Mujahid Muhammad (shown above), a Muslim convert, opposed the wars in Iraq and Afghanistan, but was not affiliated with a larger terrorist network.

photo: AP/Brian Chilson

Fort Hood Shooting

An Army psychiatrist goes on a rampage at Fort Hood, Texas, killing 13 people and wounding dozens. The alleged gunman, Maj. Nidal Malik Hasan, was a Muslim who had been in contact with a radical Imam and was about to be deployed overseas. Above, Sgt. Anthony Sills comforts his wife as they wait outside Fort Hood on the day of the shooting.

photo: AP/Jack Plunkett

IRS Plane Crash

A small jet is flown into a building housing a federal tax office in Austin, Texas, injuring 13 and killing two. The pilot, Joseph Andrew Stack, was angry with the Internal Revenue Service.

photo: AP/Jack Plunkett

Giffords Shooting

Jared Lee Loughner opens fire on then-Rep. Gabrielle Giffords, D-Ariz., while she is meeting with constituents in a supermaket parking lot near Tucson. Giffords survives but six others die.

photo: AP/Matt York

Benghazi Embassy Attack

Islamist militants attack the U.S. embassy compound in Benghazi, Libya, killing four including Ambassador Christopher Stevens and wounding 10 others.

photo: AP/Mohammad Hannon

Navy Yard Shooting

Aaron Alexis, a 34-year-old subcontractor for Hewlett Packard, opens fire in Building 197 at the Washington Navy Yard, killing 12 civilians and contractors. Alexis, killed in a shootout with law enforcement officers, was working on an upgrade to the Navy Marine Corps Intranet.

photo: AP/Jacquelyn Martin