It was the first day of summer vacation and the little girls at the Hart Space, a sanctuary hidden behind a row of houses, were there to dance to the music of Taylor Swift. What was supposed to be a day of joy turned to terror and heartbreak when an intruder with a knife attacked the girls and their teacher on July 29 in the seaside town of Southport in northwest England.

The mass stabbing in Southport, England, and misinformation about the attacker sparked days of rioting across the U.K.

An 18-year-old man pleaded guilty Monday to charges of killing three girls and wounding 10 other people in a stabbing rampage at a Taylor Swift-themed dance class in England last summer.