Britain’s political leaders sparred Sunday over who is responsible for the early release of a convicted extremist who launched a stabbing attack in central London that left two dead and injured three.

Neil Basu, London’s police counterterrorism chief, said 28-year-old Usman Khan was attending a program that works to educate prisoners when he launched Friday’s attack just yards from the site of a deadly 2017 van and knife rampage.

Dramatic video captured at the scene shows three men armed with a fire extinguisher and a large narwhal tusk take the man to the ground.