CORRECTION Grandparents Killed

These booking photos released by the Sterling Police Department show Brendan Lee Johnson, left, and his girlfriend, Cassandra Ann Rieb, arrested on suspicion of murdering his grandparents in Sterling, Colo.

(AP Photo/Sterling Police Department via The Daily Camera)

DENVER -- A couple described by one of their relatives as "young, stupid and selfish" have been accused of killing the man's grandparents so he could get his inheritance: an inexpensive house and $20,000, according to court records.

Police say Brendan Lee Johnson, 19, and his girlfriend, Cassandra Ann Rieb, 18, sneaked into his grandparents' home last month in Sterling, a small city on Colorado's rural northeastern plains, and strangled Charles and Shirley Severance, both 70.

The couple then tried to cover their tracks, scattering the grandmother's burned remains in two states and later calling 911 to report finding the grandfather's body, which was too heavy for them to dispose of as planned, authorities said. They appeared in court Wednesday, a day after being arrested.

The teens told authorities they had planned since early May to smother the Severances with pillows as they slept, but the effort became complicated when the couple put up a struggle.

"They're young stupid and selfish," said Shirley Severance's half-sister, Norma Curl. In an interview with The Associated Press, Curl said Johnson recently graduated from high school and had been living with his grandparents, but she didn't know why.

Police said the teens told them the killings happened May 20. When authorities discovered Charles Severance's body nine days later after receiving a medical call from Johnson, his wife was missing. Investigators on Monday discovered some of her remains near Sterling and others about 30 miles away in Lorenzo, Nebraska.

"Together we went and we did it together," Rieb told investigators, according to the court documents. "We had agreed to do it together, obviously. ... Like one get one and one get the other."

Rieb said the plan was to hasten Johnson's inheritance, which included the grandparents' low-slung home, valued at just $47,000.

The teens crept into the home early in the morning, but Charles Severance was awake and fought Johnson, according to the documents. Johnson told authorities he tried to choke his grandfather, who he believed then died of a heart attack.

Shirley Severance asked, "Why are you doing this to me?" and offered the combination to her safe as Johnson and Rieb strangled her, the records said. As she attempted to open the safe, Johnson grabbed a kitchen knife and stabbed his grandmother, authorities said.

In the days that followed, the couple told police that they cleaned the home, gathered up evidence and drove to Nebraska, the documents say. They said they had planned to cut up and burn both bodies, but left Charles Severance's behind because it was too heavy, the records say.

They burned Shirley Severance's body in a fire pit near Sterling but later dug it up and took some remains to Nebraska, police said.

Johnson's attorney, Rachel Lanzen, did not return calls seeking comment Wednesday, and it was unclear who would be representing Rieb. Jill Johnson, Brendan's mother and Shirley Severance's daughter, declined to comment to The Associated Press on Wednesday and asked for privacy. Calls to possible listed phone numbers for Rieb went unanswered or messages were left that weren't immediately returned.

A judge on Wednesday advised the teens of possible charges, which could include first-degree murder, aggravated robbery, forgery and theft. Both were held without bond.

Curl, Shirley Severance's half-sister, said the case surprised her -- except for one detail.

"The one thing I knew was my sister would put up a fight," Curl said.