In this city often called “the capital of Europe,” the main departures hall at Brussels Airport was a typical hive of activity Tuesday morning. A babble of languages filled the hall, as passengers milled at check-in counters. There was a line for steaming java at Starbucks.

Didier Marchal, 42, a former Belgian commando happy to be home after attending a wedding in Canada, had just gone through customs shortly after 8 a.m. Then, he heard it.

“The sound was devastating,” he recalled.

“Have you ever heard dynamite go off?” he said of the first of two explosions at the airport — which Belgian authorities described as the work of suicide bombers. A third attacker whose bomb apparently failed to explode was still at large. “This was concussive. You felt air moving toward you. It went everywhere. It took out the ceiling.”

The moments after, he said, were reminiscent of his stints in war zones, and everything around him seemed to be occurring in slow motion. “People who died weren’t whole anymore,” he said. “They were in pieces. The concussions of the blast just tore them to shreds.”

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Panicked passengers, some wounded, rushed away from the blast, only to be stopped in their tracks as a second, larger bomb went off. In the grisly scene that unfolded, captured by social media, Sebastien Bellin, a 37-year old Brazilian Belgian basketball player, lay in agony on the floor, smeared in blood. Nails and other projectiles apparently packed into the bomb had ripped through clothing, leaving one bleeding man on the ground in a shredded suit.

A woman in a yellow jacket, one shoe missing and her feet bloodied, sat shell­shocked on a bank of airport chairs. A single baby stroller stood in a cloud of dust. Panels fell from the ceiling. Smoke poured through shattered, twisted window frames.

Authorities said at least 11 people were killed.

“I saw people at the Starbucks with blood on their faces and I got really scared,” said Tatyana Beloy, a 31-year-old Belgian actress who was leaving on vacation. “I immediately ran outside. I had no clue what was happening.”

This is what was happening: For the second time in 4 1/2 months, Europe was facing a multi-pronged terrorist attack that would paralyze one of its major cities. So soon after a cell loyal to the Islamic State had killed 130 people in Paris, the militant group claimed to unleash its operatives in a wave of terror targeting the very heart of the European Union.

Brussels. The “Washington of Europe.” The administrative capital and home to thousands of office workers and officials charged with running the continent’s bureaucracy.

The Belgian government is facing a real and potent threat coming from within its borders. Here's why extremists are finding root in the country. (Jason Aldag,Greg Miller,Adam Taylor/The Washington Post)

About 75 minutes after the airport attack, assailants struck again.

Rushing to work, Charlotte Vandriesen, a 26-year-old researcher for Belgian news outlet VRT, had just made it on board her metro train before the doors closed. The train moved forward for a few minutes, she said, before she heard a large explosion and saw a cloud of dust through the windows.

“The car stopped, we were all afraid,” she said. “For a couple of minutes it was like that, people screamed. . . . So many people were crying. We all knew immediately what was going on. We had heard the news that an hour earlier there was the attack at the airport. We knew it was linked to this.”

Up ahead, only one stop away from the one used by the employees at the European Union and European Commission headquarters, an explosion had gone off on board the train that was pulling into the station. The blast killed at least 20 people and wounded more than 80.

Orry Van De Wauwer, who works for Belgium’s centrist CD&V party, was inside a building across the street. He heard the blast and felt the structure shake before he saw dozens of injured people pour out of the station.

On a day when many Belgians were called on to be impromptu emergency responders, he jumped into coordination mode. Van De Wauwer and others helped the wounded into their office building, and went desk to desk among employees asking for those who knew first aid. The political worker collected water bottles and blankets, and tended to a wounded mother with a 5-year-old boy. “She kept telling him to keep his eyes closed, not to look around,” Van De Wauwer said. “She did not want him to see what was happening around him.”

Back at the airport, planes that landed just after the explosions were forced to sit on the tarmac for hours. Passengers who had already disembarked found themselves trapped for hours, with no explanation from officials or airline representatives, they later said.

By Tuesday afternoon, many travelers from the airport were sent to a sports facility in the town of Zaventem, adjacent to the airport. At the sports hall, Marchal, the former commando, recalled the mayhem of the morning. The military and police forces­ on hand, he said, hurried passengers out of the terminal and told them to wait.

“They were actually yelling at us,” he said, adding: “The people who panicked the most were the police and the military. They were running around like chickens with their heads cut off for 15 minutes. You’d think they’d have planned for something like this, and if not, have a plan put in place.”

By dusk Tuesday, passengers had finally started to trickle out of the hall, mostly staffed by volunteers from the community, who brought bread, Easter chocolate and fresh coffee.

Miriam, a 63-year-old woman who declined to give her last name, emerged with her husband. They had both been in the terminal at the time of the explosions. Her husband was heading to Bermuda, and she was seeing him off. She had waited after he passed security to make sure he took off safely and was catching up on newspaper reading when the bombs went off.

“It was one of those hours where you realize your life can really take a turn,” she said.

“We feel so lucky,” she said, eyes welling with tears.

“Tomorrow is my birthday.”

Annabell Van den Berghe contributed to this report.

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