Tate Museum balcony
© Yui Mok/PA Wire via ZUMA PressA police officer looks out from the viewing platform at the Tate Modern art gallery in London after a six-year-old boy was thrown from the tenth floor viewing platform, Aug. 4, 2019.
A 6-year-old boy is in a critical but stable condition after being thrown five stories from the Tate Modern in London, the U.K.'s most popular tourist attraction.

The boy was visiting the modern art gallery's 10th floor viewing platform with his mother Sunday when he was taken from her arms and thrown over the railing, according to the Daily Mail. He landed on the roof of a five-story building below.

Police were called at around 2:40 p.m. local time and were accompanied by the London Ambulance Service and London's Air Ambulance. The boy was treated at the scene and then taken to the hospital by air ambulance.

A witness told the BBC that they heard a "loud bang" after the child was thrown.

BBC journalist Olga Malchevska happened to be on the viewing platform with her own child at the time. "People started to push each other," she said. "Then I saw that woman who was running and shouting, 'My son, oh my son.'"

Malchevska said that railings around the platform reach shoulder height and that there was no reason to think that the platform was unsafe.

The police arrested a 17-year-old male on suspicion of attempted murder. He remains in police custody.

"We were close to the viewing gallery on the tenth floor, that's where he was pushed," Tate visitor Nancy Barnfield told the Telegraph. "Then there was a loud bang and people rushed in to restrain him, it was mostly men. They held him for ten minutes before police arrived. His face showed no emotion, he was completely silent."

The police said there was no reason to suspect that the teenager was known to the victim.

"Tate is working closely with the police," a gallery representative said on Twitter. "All our thoughts are with the child and his family."

The gallery was closed for the remainder of Sunday. It re-opened Monday morning, but the Level 10 viewing platform remained closed.

Last year the Tate Modern became the most visited tourist attraction in the U.K., welcoming 5.86 million people in 2018, according to the Association of Leading Visitor Attractions.

Sunday's incident is similar to one that occurred in Minnesota in April when a child was thrown off the third floor balcony of the Mall of America. The victim spent almost four months in intensive care before being moved on Aug. 2 to an inpatient physical rehabilitation program at another hospital.