Singer Taylor Swift is “in “shock” after a mass stabbing that killed three children at an event to celebrate her music.

The incident happened Monday at a Swift-themed event at a property in Southport, a seaside town about 20 miles north of Liverpool, in the United Kingdom, per ABC News.

Officers responded just before noon, according to Merseyside police.

Three girls died as a result of the attack.

Bebe King, 6, Elsie Dot Stancombe, 7, and Alice Dasilva Aguiar, 9, were killed. Nine other children and two adults were injured, Merseyside police said.

Those injured remained in critical condition Tuesday, police said.

“We believe that the adults who were injured were bravely trying to protect the children who were being attacked,” Merseyside Police Chief Constable Serena Kennedy said Monday.

The motive for the attack is not clear, Kennedy said.

A flyer for the two-hour event referred to the event as a “Taylor Swift Yoga and Dance Workshop.” It was open for children between 6 and 11 years old, according to the organizer’s Instagram.

Swift responded to what happened, sailing she was “completely in shock.”

“The loss of life and innocence, and the horrendous trauma inflicted on everyone who was there, the families and first responders,” she said. “These were just little kids at a dance class. I am at a complete loss for how to even convey my sympathies to these families.”

A 17-year-old boy, whose name was not released, was arrested on suspicion of murder and attempted murder, police said.

The teenager is from Banks, a coastal village in Lancashire, just outside Southport.

Prime Minister Keir Starmer said the “whole country” was deeply shocked by the “truly awful” attack. King Charles III said he was “profoundly shocked” by the “utterly horrific incident,” CNN reported.