Illinois State Police note new lead, but still no suspect, related to 1992 murder of Tammy Zywicki

Illinois State Police and the FBI announced this weekend that they may have a new lead, though not a suspect, in the 1992 murder of college student Tammy Zywicki.

In late August 1992, Zywicki had been driving back to Grinnell College in Iowa after dropping off her brother at Northwestern University when her car broke down. She had last been seen with her car on Aug. 23, 1992, near mile marker 83 on Interstate 80, just a few miles outside Ottawa in LaSalle County.

Two days later, Zywicki's 1985 Pontiac T1000 was found abandoned on Interstate 80. She herself was nowhere to be found.

On Sept. 1, 1992, a truck driver found a body that turned out to be that of the 21-year-old Zywicki on the side of Interstate 44 near Mount Vernon, Missouri. Zywicki had been brutally stabbed to death, and had also been sexually assaulted.

The case has never been solved.

At the time of Zywicki's murder, a semi-trailer truck was seen near her disabled car, with a truck driver described as a white male between the ages of 35 and 40, over 6 feet tall, with dark, bushy hair.

There remains no information about the truck driver. But special agents are looking for information about a person they believe may have been connected to the truck driver.

Thersa "Teri" Belenske, maiden name Vega, was known to hitchhike and may have been traveling with the unknown truck driver at some point before Zywicki's death.

Belenske is dead now. She died in 2014 at the age of 54. At the time of Zywicki's murder, she would have been 32.

State police released a photo of Belenske from 2009, and an AI-generated image of what she might have looked like in 1992.

Belenske is not a suspect, but only a person of interest, state police said. Special agents are looking for information about her from the late 1980s through the mid-1990s, and noted that she had ties to California — including Oceanside, Vista, Pomona, San Bernardino, and Fontana.

34 years with zero answers in Tammy Zywicki's murder

As documented in Channel 2 News reports at the time, Zywicki's name first appeared in the headlines on Aug. 25, 1992, two days after she was last seen alive, when her car was found abandoned. Zywicki's parents had flown in from their home in Marlton, New Jersey to help police with the investigation.

"It's really just one of those surreal things when you're in it. You know, nobody expects to be in a situation like that. It's hard to recollect back that long, but it's one of those where every day would go by – it's like it's not real, essentially," Dean Zywicki told producer Dylan Van Sickle for a 2023 CBS News Chicago documentary. "Like you push the reality aside just trying to focus on finding her."

Former CBS News Chicago anchor and investigator Brad Edwards talked in 2022 with Tammy Zywicki's friend, Jen Dowd Nelson. Edwards asked Nelson if she hypothesizes about what happened to Zywicki.

"I don't hypothesize if I can help it, because it's ridiculously frightening," Nelson said.

In the ensuing days, Zywicki's family held out a sliver of hope that she might be alive, as did her classmates at Grinnell, who held candlelight vigils in hopes that she would be found alive.

But a body that turned out to be Zywicki's was found nine days after she had last been seen alive.

Investigators did not believe Zywicki was killed near where her body was found along I-44. They believed that she was stabbed to death someplace else, and that the killer had been driving the body for some time across Illinois and Missouri, before dumping the body into the underbrush along the access road on I-44.

"I also didn't have any experience at 20 years old and 21 years old knowing, or understanding, how somebody could be so horrible, and hurt somebody like that," Nelson told Edwards.

In the days following the discovery of Zywicki's body and the confirmation of her identity, a nationwide search commenced, with everyday people joining to help in the search. The nonprofit Iowa Cold Cases noted that authorities launched a multistate task force with 14 investigators from both local forces and the FBI.

Several suspects were identified. Lonnie Bierbrodt, a trucker and a felon on parole, was questioned early in 1993 and had blood and hair samples taken. In 2014, former Illinois State Police investigator Martin McCarthy told the late CBS News Chicago reporter Mike Parker that Bierbrodt was placed in LaSalle County the day Zywicki disappeared, and one witness identified him as the man she saw standing alongside Zywicki on the highway.

Bierbrodt also lived near the scene where Zywicki's body was found, McCarthy noted.

But while McCarthy said in 2014 that he believed Bierbrodt was the killer, Bierbrodt ended up being released for a lack of evidence. The task force disbanded in February 1993, according to Iowa Cold Cases. Bierbrodt died in 2002.

Meanwhile, there were follow-up stories across the news media in the months and years after Zywicki was murdered. Other names came up as possible people of interest in the Zywicki case over the years, only to be ruled out. There was nothing to point to a killer, and the case went cold.

But those who care have never given up. In 2009, the "Who Killed Tammy Zywicki" Facebook group went online, and it remains as active as ever today.

"I'd seen it in the paper, and it just stuck with me all those years, and then when Facebook popped up, I decided, why not? You know, give it a shot," group administrator Patrick Jones told CBS News Chicago for our 2023 documentary. "We had like 60 members at one time."

As of Aug. 23, 2026, there were 7,780 members, up from 5,725 three years earlier.

In recent days, administrators for the group have noted the new lead involving Belenske, and a new Illinois State Police podcast on the case. Former CBS News Chicago anchorman Bill Kurtis, who is seen on the anchor desk in much of the archive video on the Zywicki case, is the narrator for the podcast.

Anyone with information about Belenske and whom she may have traveled with in the late '80s or early '90s is asked to go to the ISP Investigative Tips page or call 1-800-CALL-FBI.  Callers may remain anonymous.

Anyone with information about Zywicki's murder is asked to contact the ISP or FBI at the above number and page, or the Who Killed Tammy Zywicki Facebook group.

The FBI is offering a reward of $50,000 for information leading to the identification of the person or people responsible for Zywicki's murder.

Video above: "Who killed Tammy Zywicki? Over 30 years, zero answers," from August 2023