19-year-old Brendan Lee Johnson and 18-year-old girlfriend Cassandra Ann Rieb appeared in Logan County Court Wednesday after they were arrested for the deaths of Johnson’s grandparents, Charles and Shirley Severance. Johnson told police that they killed the elderly couple so he could inherit their house and money.

The Chicago Tribune reports that Johnson told investigators that he and Rieb had conspired to kill his grandparents about three weeks before the attacks. They planned to smother the elderly couple as they slept.

NY Daily News reports that Johnson told police that Charles Severance was awake when they snuck into the house. He began choking his grandfather, and claimed that he likely died of a heart attack during the fight. When they attacked Shirley Severance, they strangled and stabbed her with a kitchen knife.

NY Daily News reports that Rieb told police, “Together we went, and we did it together. Like one get one and one get the other.”

The teens burned Shirley Severance’s body, then took the remains to Nebraska. They planned to do the same with Charles Severance’s body, but they told investigators that he was too heavy too carry. Instead, they cleaned the grandparents’ Colorado home and called 911 nine days later to report Charles Severance dead and his wife missing.

The teens are being held without bond on suspicion of first-degree murder of Charles and Shirley Severance, both 70.