The first funerals have been held for some of the 42 people killed in the Istanbul airport attack.
US counter-terrorism officials believe the terrorist group involved in the triple suicide bombing contained dozens of members.
Footage of the blasts shows a sleeper cell ordered to attack. One moment, people are rushing for their flights - the next, for their lives, as gunfire and explosions break out.
It becomes clear that the absolutely unthinkable is happening all around them. The attack was like Brussels all over again, but worse - because in peeling away Istanbul's extra layer of security, Islamic State (IS) may have launched one of its most sophisticated attacks yet.
Minutes before, the attackers were just faces in a crowd; wearing battlefield black, the apparent tourists became terrorists.
It is believed the intention of the terrorists was to take hostages. One used his gun to try to smash into the departure lounge.
"I saw one terrorist break the window to the gate and run to the plane," one witness says.
One mother was so convinced she would be killed that she scrawled her daughter's details on her arm to help someone locate her.
At the entrance to the international terminal, people must go through x-ray machines before the first security checkpoint. That's the place the terrorists are believed to have started shooting.
After an exchange of gunfire with police, two of the attackers blew themselves up in the terminal - one in arrivals, the other next to a departure gate. Another is believed to have detonated his device in the airport's carpark.
Identifying IS as the likely culprits, Turkish prime minister Binali Yildirim says: "Terror is a threat to all countries - they must work together against terrorism".
However it's a threat to Turkey more than most. The airport should have been one of the safest places in the country, but the gateway of choice for IS fighters became the target for one of the most extraordinary assaults.