One Of The Hillside Stranglers Killed Outside L.A. Too — Who Were Kenneth Bianchi’s Other Victims?

When most people think about the Hillside Strangler case, they think about the 10 murder victims killed and left on the hills of  Los Angeles. But one of the killers killed beyond the city limits, murdering two additional victims in Washington State.

Kenneth Bianchi and Angelo Buono impersonated off-duty police officers to lure victims to their death, often after the sun went down. In all, the pair murdered 10 women and girls between October 1977 and February 1978 during their California spree.

As seen in “The Hillside Strangler: Devil in Disguise,” a new four-part Peacock docu-series streaming now, Bianchi also preyed upon women in Washington. After the California killings, he moved to the Pacific Northwest, where he killed once again.

While working as a security guard in Washington, he lured two Western Washington University students, a pair of roommates, to their death. Karen Mandic, 22, and Diane Wilder, 27, became his final victims on January 11, 1979. They were found dead inside the hatchback of Mandic’s car parked in a remote part of Bellingham, Washington, a day later.

Both victims had deep furrows on their necks, indicating that they had been the victims of strangulation via ligatures. Investigators believed they were sexually assaulted and killed at another location, and then re-dressed before being dumped in the car’s hatchback.

One of the victims, Karen Mandic, worked at a local Fred Meyers, a Pacific Northwest grocery chain, in Bellingham, where she met Ken Bianchi, who worked at the store for a time as a security guard. Both Wilder and Mandec were embarking on a housesitting gig that had been arranged by Bianchi when they vanished. The job, which would have landed them $100 apiece, was only supposed to take two hours. But when Karen Mandic did not return from her dinner break, her employer became concerned. The police were contacted and the girls were found dead the following day.

It was the murder of these two victims that led to the arrest of Bianchi — and eventually Buono. Bianchi was linked to Mandic after investigators found his phone number and address in a handwritten note at her home. 

After working with Mandic at Fred Meyers, Bianchi had moved onto Whatcom Security, where he was working when he hired the girls to do the job they vanished from. Hours before the bodies were found, investigators went down to the security company to interview Bianchi. He lied to them initially, saying he had not spoken to Mandic for months, but investigators believed the evidence showed otherwise and that Bianchi was a prime suspect in the murders.  Soon enough he was in custody.

Investigators in Washington reached out to police down in Los Angeles as they were looking for background information on the suspected killer; L.A. detectives were then able to connect the dots, realizing that Bianchi had lived in close proximity to numerous Hillside Strangler victims. Eventually, investigators had enough information to assume that they had at least one of their Los Angeles killers. Through interviews, Bianchi implicated his adoptive cousin as an accomplice. Buono was arrested months later in October 1979.

While Bianchi initially entered a plea of not guilty by reason of insanity, he later pleaded guilty to the Washington double murder and five of the California slayings, according to the St. Louis Post-Dispatch. He was sentenced to multiple life terms and is still alive and incarcerated in the Washington State Penitentiary in Walla Walla.

Buono was convicted of nine of the 10 murders and sentenced to life behind bars, the St. Louis Post-Dispatch reported. Buono died in prison in 2002.

Learn more about the case by watching “The Hillside Strangler: Devil in Disguise,” streaming now.