An attacker with a knife killed two children and wounded 11 other people, including six youths in critical condition, at a dance class in northern England on Monday, police said. A 17-year-old male has been arrested on suspicion of murder and attempted murder in Southport, near Liverpool in northwest England, in an attack that also left two adults with critical injuries, Merseyside Police said. Police chief Serena Kennedy said that the attack was not being treated as terror-related, and that the attacker’s motivation was unclear. All of those injured had been stabbed, she added. Prime Minister Keir Starmer told the media that “the events today are just truly awful, the whole country is deeply shocked”. “Our thoughts and condolences are with the victims, families, friends and wider community. It is almost impossible to imagine the grief,” he said.