A quiet morning in Belgium turned into a nightmare when a train smashed into a school bus at a railroad crossing, killing four people, including two children.

The deadly crash happened Tuesday morning in Buggenhout, a town about 15 miles northwest of Brussels. Authorities said the bus was carrying nine people at the time: the driver, a chaperone and seven students.

Two students, ages 12 and 15, were killed. The 49-year-old bus driver and a 27-year-old chaperone also died in the horrific collision.

Five other students were rushed to the hospital with serious injuries. Officials said they were in critical but stable condition.

The children were reportedly on their way to Richtpunt campus Buggenhout, a special education school located less than a mile from the railroad crossing where the crash occurred.

The crash happened around 8:08 a.m. near the town’s train station. Officials are now trying to figure out how the school bus ended up in the path of the oncoming train.

Thomas Baeken, a spokesperson for rail track operator Infrabel, told local media that footage from the scene showed the railroad barriers were down and the traffic lights were red.

“The collision took place at 8.08 a.m. Footage shows that the barriers were down and the traffic lights were red,” Baeken said, according to VRT NWS. “We do not know how the accident could have happened.”

He said the train driver tried to stop in time.

“The train was already braking. The train driver did apply the emergency brake, but was unable to avoid a collision,” Baeken said.

Investigators are now focusing on why the bus continued through the crossing despite the warning signals. Infrabel said it will fully cooperate with the police investigation.

There were about 100 passengers on the train at the time of the crash. No one on the train was killed or physically injured, though one person was taken to the hospital for shock.

Photos from the scene showed emergency crews swarming the area as the damaged train sat near the crossing. The crash also caused train cancellations, with replacement buses brought in for stranded passengers.

Belgian officials expressed heartbreak after the tragedy.

Transport Minister Jean-Luc Crucke said his “first thoughts” were with the victims, the injured and their families.

Belgian Prime Minister Bart De Wever called the crash a “horrific accident” and said his thoughts were with the devastated families.

Buggenhout Mayor Geert Hermans said the local community had been “hit hard” by the tragedy and thanked emergency workers for rushing to the scene.

Belgium’s interior minister Bernard Quintin also shared condolences, saying he learned of the fatal crash with “great dismay.”

“My thoughts go out to the victims and their loved ones. I wish the injured much strength,” he wrote on X.

Ursula von der Leyen, the Belgium-born president of the European Commission, said she was “heartbroken” by the tragedy.

“My deepest condolences go out to the victims’ families and their loved ones,” she wrote. “Today, Europe grieves with Belgium.”

The investigation remains ongoing as authorities work to determine exactly what led to the deadly collision.