By Belinda Robinson and Snejana Farberov A teenage couple from Colorado accused of murdering the boy's grandfather and killing and dismembering his grandmother for his inheritance could face the death penalty. Prosecutors are actively seeking the maximum penalty for Brendan Johnson, 20, and his girlfriend, 18-year-old Cassandra Rieb from Colorado, who allegedly strangled Charles and Shirley Severance, both 70, to death at their home in Sterling in May. Police say Rieb told them Johnson wanted to inherit their house and $20,000 from their checking account. Scroll down for video 'Criminal duo': Brendan Johnson, 19 (left), and his girlfriend, Cassandra Rieb, 18 (right), could face the death penalty for allegedly murdering the boy's grandparents in order to get their hands on $20,000
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Prosecutors seeking the death penalty for Brendan Johnson, 20, and Cassandra Rieb, 18, from Colorado
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They are charged with killing Johnson's grandparents Charles and Shirley Severance, both 70
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Police say Johnson repeatedly stabbed and then strangled his grandmother with a string before burning her body
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Shirley Severance's remains were found in two separate locations more than a week later
Before she died, Shirley Severance reportedly asked her attackers ‘why are you doing this to me?’ according to @placeholder.