Report: Teens Brendan Johnson and Cassie Rieb burned, tried to dismember his grandma's body

Update: Our original post about the arrest of Sterling teens Brendan Johnson and Cassandra Rieb for allegedly murdering his grandparents, Charles and Shirley Severance, contained plenty of unsettling information; see our previous coverage below. But claims from a newly released arrest affidavit in the case are infinitely more shocking.

Among the assertions: Shirley begged for her life while being repeatedly stabbed, and after she was killed, Johnson and Rieb tried but failed to chop up her body while she was being incinerated. Moreover, the murders were committed nine days before they were reported. Additional photos and details below.