Catherine Marie Tornquist, 56, of rural Hot Springs, South Dakota, was last seen on the evening of October 4, 2011, when a friend dropped her off in the parking lot of Sonny's Super Foods in Hot Springs after the two had spent the day sightseeing. Tornquist was planning to drive to Rapid City the next morning to complete the purchase of a motor home, on which she had already placed a $1,000 deposit, and was reportedly carrying approximately $10,000 in cash. She never arrived. Her son, Matthew Tornquist, told investigators his mother woke him that morning and said she was leaving for Rapid City. Fall River County's sheriff contacted the South Dakota Division of Criminal Investigation on October 7, 2011, the same day a friend reported Tornquist missing. The contents of her purse were later found discarded along a gravel road northeast of Buffalo Gap, South Dakota.
The South Dakota Division of Criminal Investigation led the inquiry. Investigators found blood and two spent .22-caliber bullets in Tornquist's bed, a bloodstained sheet of plywood on her property, and a partially burned cell phone in a burn barrel. A stolen .22-caliber rifle recovered from Matthew Tornquist's dormitory room at National American University in Rapid City carried skin cells matching Catherine Tornquist's DNA, and her blood was found on a pair of his jeans. Matthew Tornquist was indicted in July 2012 on charges of first-degree murder, second-degree murder (alternative count), and grand theft, and was convicted by a Pennington County jury in July 2014 after roughly two hours of deliberation; he was sentenced to life in prison without parole plus 10 years on the theft count, and the South Dakota Supreme Court affirmed the conviction and sentence in 2015. He has consistently maintained his innocence. More than 50 land, air, and water searches have been conducted, and Catherine Tornquist's body has never been located. The case remains open with respect to locating her remains. NamUs Case Number: MP17828. Agency Case Number: 1104977. Anyone with information is asked to contact the South Dakota Division of Criminal Investigation.
