1992 kidnapping and murder case remains active as authorities seek person of interest

Authorities are seeking information about a person of interest in an unsolved 34-year-old kidnapping and murder case.

Tammy J. Zywicki went missing Aug. 23, 1992, while on her way back to college in Grinnell, Iowa, after dropping her brother off at Northwestern. The New Jersey native was last seen that same day between 3 and 4 p.m. in LaSalle County with her broken-down car, according to Illinois State Police, which continues to investigate her death in partnership with the FBI.

Her car — a 1985 White Pontiac T1000 — was found abandoned by an Illinois trooper and was towed the following day, Aug. 24. That night, Zywicki’s mom reported her 21-year-old daughter missing. About a week later — on Sept. 1 — Zywicki was found stabbed to death in a ditch on I-44 in rural southwestern Missouri.

A semi-truck was seen near Zywicki’s car around the time she disappeared, according to state police. The truck driver was described as a white man between 35 and 40 years old and over 6 feet tall with dark hair.

Investigators are now looking into a person of interest who may have been hitchhiking with that truck driver before Zywicki’s murder.

Theresa “Teri” Belenske — maiden name Theresa Vega — would have been 32 years old at the time and was known to hitchhike, state police say. Belenske, who died in 2014, is not a suspect, but investigators are seeking information about Belenske from the late 1980s to mid-1990s. She had ties to several California cities, including Oceanside, Vista, Pomona, San Bernadino and Fontana.

ISP shared a 2009 photo of Belenske and an AI-generated image of what she may have looked like in 1992.

Anyone with information about Belenske or Zywicki’s murder can submit a tip to isptips.illinois.gov or call 1-800-CALL-FBI. The FBI continues to offer a $50,000 reward for information that leads to the identification of who was responsible for her murder.