It was one of the first days of summer break, and a group of young girls was dancing to Taylor Swift songs in a studio on a quiet street in Southport, in northwest England.

As the class, which also included yoga and bracelet making, was drawing to an end on Monday morning, an attacker walked in and rampaged through the room with a knife, stabbing the children and two adults.

Two girls — Bebe King, 6, and Elsie Dot Stancombe, 7 — died of their injuries on Monday, the Merseyside Police said in a statement, while a third, 9-year-old Alice Dasilva Aguiar, died in the hospital early Tuesday. Eight other children were injured, five of whom remain in critical condition in the hospital, along with two adults who had tried to protect them, the police said.

The question of why such an unremarkable summer morning, filled with dancing and fun, had turned to horror was on the minds of many residents of Southport, a seaside town of about 95,000 people, on Tuesday as they grappled with the violence that had visited their quiet community.

“It was just little girls who wanted to dance,” said Carol Sansom, 76, who had come with her husband to lay flowers on Hart Street, where the class was held. They have lived in the neighborhood for more than five decades and described it as a residential place where they raised four children.