Tammy Zywicki

On August 23, 1992, 21-year-old Tammy Jo Zywicki was driving from her family's home in New Jersey to Grinnell College in Iowa for the start of her junior year. Her car, a white 1985 Pontiac T-1000, broke down on Interstate 80 near the LaSalle-Peru exit in LaSalle County, Illinois. Multiple witnesses reported seeing Tammy standing by her disabled car, and several reported seeing a semi-truck—variously described as white with a rust-colored or tan cab—parked behind her vehicle.

When Tammy did not arrive at Grinnell College, her family contacted authorities. Her car was found on the shoulder of I-80 with the hazard lights still on. On September 1, her body was found wrapped in a blanket and a red sleeping bag along the shoulder of Interstate 44 in Lawrence County, Missouri, approximately 500 miles from where her car had been found. She had been stabbed.

The FBI joined the investigation and focused on the semi-truck seen near Tammy's car. A composite sketch of the truck driver was created from witness descriptions, and the sketch was distributed nationwide. The case was featured on America's Most Wanted and generated thousands of tips. Long-haul truckers were extensively investigated.

Despite one of the most intensive FBI investigations of a highway murder, the killer has never been identified. The FBI investigated the possibility that Tammy's murder was connected to other unsolved highway murders of young women during the 1990s, including cases attributed to possible serial killers operating along the interstate system. The FBI continues to seek information about the semi-truck and its driver.