Taylor Swift said she was “in shock,” as police said the event was Swift-themed.

Police said three children have died and several other people were injured in a stabbing attack in the United Kingdom.

LONDON — Police investigating the deadly attack on a children’s music event in a seaside town of Southport, United Kingdom, said they would interview the 17-year-old suspect as they searched for a motive.

“The investigation is in its early stages and the motivation for the incident remains unclear,” Merseyside Police Chief Constable Serena Kennedy said on Monday.

Officers responded just before noon local time to reports of a stabbing at a property on Hart Street in Southport, a seaside town about 20 miles north of Liverpool, according to Merseyside Police.

Three children were killed and nine others were injured in a stabbing attack at an event at a dance school in the seaside town, police said. Five of the wounded children were in critical condition, along with two adults, who were also stabbed, police said.

Alice Dasilva Aguiar, 9, died early Tuesday from her injuries, and Elsie Dot Stancombe, 7, and Bebe King, 6, died Monday, police said.

“Keep smiling and dancing like you love to do our princess,” Aguiar’s parents said in a statement released by police. “Like we said before to you, you’re always our princess and no one would change that.”

King’s family said no words could describe their devastation at the loss “of our little girl Bebe.”

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

The “horror” of the attack was “washing over me continuously,” Swift said in a post on Instagram. She said 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 from Banks, a coastal village in Lancashire, just outside Southport, was arrested on suspicion of murder and attempted murder, police said.

The suspect, whose name was not released, was born in Cardiff, Wales, police said.

The “full circumstances” were still being investigated, she said, adding that the attack wasn’t being investigated as a terror-related. Police were not searching for additional suspects, they said.

A group of Swift’s U.K. fans calling themselves “Swifties for Southport” launched an online fundraiser to help families of the victims. It raised over 100,000 pounds ($128,000) within 24 hours.

Britain’s worst attack on children occurred in 1996, when 43-year-old Thomas Hamilton shot 16 kindergartners and their teacher dead in a school gymnasium in Dunblane, Scotland. The U.K. subsequently banned the private ownership of almost all handguns.

AP News contributed to this report.