By Keith Coffman
DENVER (Reuters) - A Colorado teenager accused of murdering his grandparents told police he enlisted his girlfriend to help kill the elderly couple so he could inherit their house and money, according to arrest affidavits released on Wednesday.
Brendan Lee Johnson, 19, and Cassandra Ann Rieb, 18, are being held without bond on suspicion of first-degree murder for the slayings of Charles and Shirley Severance, both 70.
Charles Severance was found dead at his home in Sterling, about 110 miles (117 km) northeast of Denver, in late May.
His wife was missing until this week when one set of Shirley Severance's dismembered remains was discovered at a reservoir outside Sterling, and a second set was located across the state line in Nebraska, police said.
Johnson and Rieb made their first court appearances in Logan County Court on Wednesday to be advised of the potential charges, which also include felony theft, forgery, and burglary.
The grisly details of the couple's murders were outlined in affidavits filed by a Sterling police detective in support of the arrests, in which the pair each confessed to the slayings.
Johnson told investigators he wanted his grandparent's house, and Rieb said Johnson told her he also stood to collect $20,000 from their checking account, the affidavits said.
Johnson told investigators he and Rieb had plotted to kill his grandparents about three weeks before the attacks, and the plan was for them to smother the elderly couple as they slept.
As he choked his grandfather, the man convulsed and stopped breathing, Johnson told detectives.
"He (Johnson) stated he didn't kill his grandfather, he died of a heart attack," the affidavit said.
Johnson also said that Shirley Severance had begged for her life, and told her attackers she would give them money.
Johnson said he tried to slit her throat, and that he and Rieb stabbed and strangled the woman until she died.
He and Rieb then burned her body and buried her near the reservoir. When they went back to move the body, it was in pieces and they dumped some remains near Lorenzo, Nebraska.
Rieb led police to the site where investigators said they found a "burned torso and head," the arrest affidavit said.
(Editing by Daniel Wallis and Sandra Maler)