On Sept. 11, 2012, heavily armed Islamist militants launched an organized attack on the U.S. diplomatic mission in Benghazi, Libya, setting fire to buildings before all U.S. personnel could escape or reinforcements could arrive. The attackers later launched mortar rounds at a nearby CIA compound. Ambassador J. Christopher Stevens and three other Americans were killed in the violence, making it the first time since 1979 that a U.S. ambassador was killed in the line of duty. On June 15, 2014, U.S. Special Operations forces captured one of the suspected ringleaders of the attacks.

Here is how the events played out.

Sept. 11, 2012

9:40 p.m.: Unidentified gunmen launch an assault on the U.S. diplomatic compound in the eastern Libyan city of Benghazi, quickly overwhelming the U.S. and Libyan forces who were providing security. Inside the compound, security forces are separated from U.S. Ambassador J. Christopher Stevens. U.S. personnel who retreat to another building come under siege for two hours before a CIA security team and some Libyan security forces repel the attackers.

10:30 p.m.: Stevens and State Department information management officer Sean Smith have taken refuge in the main building in the compound, behind a fortified door with metal bars that keeps the attackers from breaking in. But the militants set fire to the building. Within minutes, Stevens and Smith are overwhelmed by smoke.

11 p.m.: A U.S. surveillance drone arrives over Benghazi. Then-Defense Secretary Leon E. Panetta and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, meet with President Obama.

1 a.m.: A U.S. rescue team arrives in Benghazi from Tripoli, Libya’s capital. Nearly 30 Americans are rescued from the compound. Shortly thereafter, Stevens is taken to Benghazi Medical Center and pronounced dead on arrival, according to a hospital source. (A Libyan doctor tells the Associated Press that Stevens died of asphyxia, probably caused by smoke inhalation.)

1:45 a.m.: The AP moves a news alert, reporting the death of at least one American in the Benghazi assault.

4 a.m.: Gunmen launch an assault using mortars against the CIA annex. Glen Doherty and Tyrone S. Woods, both former Navy SEALs, are killed. Two other Americans are wounded.

4:08 a.m.: Secretary of State Hillary Rodham Clinton issues a statement. “I condemn in the strongest terms the attack on our mission in Benghazi today. . . . The United States deplores any intentional effort to denigrate the religious beliefs of others. Our commitment to religious tolerance goes back to the very beginning of our nation. But let me be clear: There is never any justification for violent acts of this kind.”

Sept. 12, 2012

Obama announces that Stevens was among those killed in the Benghazi assault. In his statement, the president says, “I strongly condemn the outrageous attack on our diplomatic facility in Benghazi.” His statement also says: “While the United States rejects efforts to denigrate the religious beliefs of others, we must all unequivocally oppose the kind of senseless violence that took the lives of these public servants.”

October 2012

Ahmed Abu Khattala, a “senior leader” of the Benghazi branch of the militant group Ansar al-Sharia, is identified as one of the ringleaders of the attack on the diplomatic mission.