In Burj al-Barajna, a district of southern Beirut adjacent to Hizballah’s headquarters in Dahiya, at about 18:00 on 12 November 2015, a standing motorcycle laden with explosives was blown up outside a Shi’a mosque as a crowd of worshippers left after evening prayers. This was followed quickly by a suicide bomber blowing himself up among the crowd of Shi’a worshippers. A second suicide bomber blew himself up near a bakery, less than 500 yards away.
A third suicide bomber attempted to detonate amid the first-responders outside the mosque but was tackled to the ground the by 32-year-old Adel Termos, who was walking in a nearby open-air market with his daughter. The bomb vest was triggered and Termos was killed, but his daughter—and untold tens or hundreds of others—were saved. Termos left behind his wife, Bassima, 6-year-old daughter, Malak, and 2-year-old son, Akram.
43 people were massacred and 239 injured, according to the Lebanese Health Ministry the day after the attack, making it one of the deadliest acts of violence since the civil war ended in 1990. The worst previous attack in terms of casualties was on August 23, 2013, when two mosques were struck in Tripoli, killing at least 42 people and wounding hundreds.
The Islamic State claimed responsibility on November 12 and in blatantly sectarian terms. “Let the Shi’ite apostates know that we will not rest until we take revenge in the name of the Prophet,” IS said.
In Dabiq 12, released on November 18, 2015, IS wrote:
[T]he soldiers of the Khilafah in Lebanon parked a motorbike rigged with explosives on al-Husayniyyah Street in the region of Burj al-Barajinah located in the southern suburb of Beirut, a Hizbul-Lat stronghold, and detonated it on a gathering of Rafidi mushrikin. When the murtaddin subsequently gathered at the site of explosion, one of the soldiers of the Khilafah detonated his explosive belt in their midst. The operation succeeded in killing more than 40 Rafidah and wounding over 200 more, and sent a clear message to the Rafidi allies of Bashar in Lebanon that they are well within the vengeful reach of the Islamic State. May Allah accept our istishhadi brother amongst the shuhada.
A fourth suicide bomber was taken into police custody alive and revealed that the four men had entered Lebanon only two days before the attack. The Lebanese government has been unable to name the suicide-killers, but strongly suspects that two of those who killed themselves were Palestinians, recruited from the Burj al-Barajna camp, and one was Syrian.
Western counterterrorism officials believe the IS strike in Beirut was “directed from Syria and conducted by operatives on the ground.”
 Kareem Shaheen, “‘Dad is a martyr’: how Adel Termos became a saviour in Beirut bombings,” The Guardian, November 17, 2015, http://www.theguardian.com/world/2015/nov/17/adel-termos-martyr-father-became-saviour-beirut-bombings
 Joyce Hackel, “A father’s split-second heroism saved countless lives in another terror attack, in Beirut,” PRI, November 13, 2015, http://www.pri.org/stories/2015-11-13/fathers-split-second-decision-during-bombings-beirut-saved-countless-lives
 Anne Barnard and Hwaida Saad, “ISIS Claims Responsibility for Blasts That Killed Dozens in Beirut,” The New York Times, November 12, 2015, http://www.nytimes.com/2015/11/13/world/middleeast/lebanon-explosions-southern-beirut-hezbollah.html
 Bassem Mroue, “Twin suicide blasts in Beirut’s Shiite suburb kill 43,” The Associated Press, November 12, 2015, bigstory.ap.org/article/b0d3dee80df64ff19b463aeda4b512e5/explosion-heard-shiite-suburb-south-lebanese-capital
 Faith Karimi, “Beirut suicide bombings: Why Lebanon and what’s next?,” CNN, November 13, 2015, edition.cnn.com/2015/11/13/middleeast/beirut-suicide-bombings-explainer/
 Eric Schmitt, “Paris Attacks and Other Assaults Seen as Evidence of a Shift by ISIS,” The New York Times, November 22, 2015, http://www.nytimes.com/2015/11/23/world/europe/paris-attacks-isis-threatens-west.html