To date, Belgian officials have said that at least four people were directly involved in Tuesday’s terror attacks in Brussels: Khalid el-Bakraoui, Ibrahim el-Bakraoui, and Najim Laachraoui—who are all believed to have blown themselves up during the attacks—and a fourth unidentified man who may still be at large. That man was seen in airport surveillance footage walking alongside two of the other suspects shortly before the explosions. (He is the one in the photo above.)
But according to Belgian state media and two French outlets, authorities are now investigating a fifth man as well, via the Associated Press:
Belgian state broadcaster RTBF and France’s Le Monde and BFM television reported Thursday that a fifth attacker may also be at large: a man filmed by surveillance cameras in the Brussels metro on Tuesday carrying a large bag alongside Khalid El Bakraoui. RTBF said it is not clear whether that man was killed in the attack.
Images of the fifth suspect have not been released. The working theory seems to be that Ibrahim el-Bakraoui and Laachraoui detonated suicide bombs at the airport while the man in the hat escaped after abandoning his bomb, which was later found by police and detonated in a controlled explosion. Roughly an hour after the airport blasts, Khalid el-Bakraoui detonated his suicide bomb in the subway. It is unclear what the fifth man did—or if he survived—after helping el-Bakraoui carry the large bag that was presumably filled with explosions. But, again, the investigation is ongoing and this is just the closest thing to a narrative that can be crafted from the limited information that has been released and reported.
Authorities have not said how many people were involved in the Brussels attack. Ten men are believed to have directly carried out November’s terror attacks in Paris that killed 130.
Read more of Slate’s coverage of the Brussels terror attacks.
