On the evening of December 19, 1979, Martinko attended a banquet for the Kennedy Concert Choir at the Sheraton Inn in Cedar Rapids. She wore a black jersey dress and black scarf, black tights and heels, and a waist-length white and brown rabbit fur jacket, and she carried a brown leather purse. After the event, she asked her friend and twirling squad teammate if she wanted to join her on a shopping trip to the Westdale Mall, which had recently opened, and where Martinko worked. Her friend declined. Martinko then asked another acquaintance to go to the mall with her; that friend said yes at first but later changed her mind. Martinko then went to the mall alone, carrying $180 and intending to finalize the purchase of a new winter coat that was on layaway. Once there, she perused the stores and spoke with friends and other people she knew who worked there. She was last seen almost 9p.m. outside of a jewelry store in the mall. At 2a.m., since Martinko had still not returned home, her father reported her missing. He began to search for her, as did the police. At 4a.m., police found the Martinko family's tan and green 1972 Buick Electra in the northeast corner of the mall parking lot by a JCPenney. Martinko was found inside collapsed over the passenger seat and stabbed to death.
