Matthew de Grood is responsible for Calgary’s deadliest mass killing as of April 2014, when he fatally stabbed five university students at a Brentwood house party. At age 22, de Grood—son of a Calgary police inspector—attacked under the influence of an acute psychotic episode fueled by undiagnosed schizophrenia. A court later ruled him not criminally responsible (NCR), citing his mental illness as the cause. Since then, he's remained under psychiatric care, transitioning slowly through supervised settings—most recently residing in a structured group home in Calgary—and annual mental health reviews have deemed him still a significant risk, denying full discharge. His case continues to spark debate about public safety and rights under the criminal code’s provisions for those found NCR.