ISTANBUL — Three men hailed a cab from the center of Istanbul around 9 p.m. Tuesday, and headed to Ataturk Airport. After being dropped off, one of the men stood near the entrance to the international terminal, where a police officer grew suspicious and texted his colleague: "He's wearing a coat on a summer day, he looks like a burglar."

Five minutes later, the terrorists launched their attack.

At first, the officer followed the suspicious man. In front of the departures terminal, he stopped the man and asked him to show identification. The terrorist pretended to bend down to reach for it, and started to shoot. He fired three rounds and the officer was critically injured.

The terrorist then ran down a flight of steps to the arrivals terminal and out of the building, and blew himself up next to a taxi stand at 9:51 p.m. The officer who risked his life to stop the attack became a hero. His intervention helped foil the terrorists' action plan. He was taken to the hospital, where he has been fighting for his life. His wife is six months pregnant with their first child.

At the scene of the attack, the other two terrorists ran inside the international terminal. They stopped for a brief moment in front of the x-ray security check. With the sound of the first explosion, they opened fire with their Kalashnikov rifles. While one shot people on the right side, the other targeted those on the left while they both kept walking. It's at that point that the second police officer, who had earlier been alerted by his colleague, returned fire.

"I took cover and started shooting. A gunfight ensued. I shot him. I continued shooting when he fell down but I couldn't shoot him in the head. He was moving on the ground. At that moment I understood that he was a suicide bomber and threw myself behind a pillar. He pulled the pin and blew himself up," the officer recounted. He was also taken to the hospital.

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A CCTV image of one of the suspected attackers

The third terrorist, while firing at everyone around him, ran down a staircase. On the ground floor, a customs officer intervened and the terrorist detonated his suicide vest.

The quick action of the two police officers and their attention to detail prevented a larger massacre. The whole attack — shootings, gunfight with police, explosions — lasted three to four minutes.

The terrorists themselves may not have been Turkish. From the taxi driver's statement, it appears they were not Arab. One of them might be from Dagestan (in the north Caucasus region). Their origins are still under investigation: Did they come from Syria or was this attack planned and executed within Turkey by operatives from the Islamic State (ISIS) terror group? The terrorist from Dagestan apparently came in a plane from another country.

The investigation is reviewing 361 surveillance cameras. In early June, the Turkish National Intelligence Organization alerted authorities of a possible ISIS attack on the airport. After this warning, security precautions at the airport doubled. That's why the terrorists were not able to actually infiltrate the main airport building.

The terrorists were familiar with the airport, especially the international terminal, meaning they probably went to survey it before the attack. The trio left behind two Kalashnikov automatic rifles, two Glock semi-automatic pistols, a grenade and a suicide vest.