05/27/2026
Sonoma County Sheriff’s Office Closes 1983 Cold Case Homicide of Robert Pangborn
The Sonoma County Sheriff’s Office has officially closed the 1983 homicide investigation into the murder and sexual assault of Robert Pangborn. He was 31 at the time of his death.
On May 21, 1983, deputies began a homicide investigation after Pangborn was found murdered on Riverlands Drive in Guerneville. He was discovered partially clothed and had suffered a fatal stab wound.
During the original investigation, detectives collected and preserved physical evidence. Investigators conducted an extensive investigation, but despite their efforts, no suspect was identified at the time. DNA technology was not yet available to law enforcement.
Cold cases at the Sonoma County Sheriff’s Office are continually reviewed as advances in forensic science create new investigative opportunities. Between 2010 and 2023, evidence from this case was submitted to the Santa Clara County Crime Laboratory and later the Serological Research Institute for advanced DNA testing. As new methods became available, additional testing was conducted in an effort to identify a suspect.
In 2024, through a DNA match, detectives identified Oscar Bolanos, 67, as a suspect in the sexual assault and killing of Robert Pangborn.
In 1992, Bolanos was arrested in Los Angeles County for the so**my and sexual assault of a juvenile and was sentenced to state prison. As part of that case, his DNA was collected and entered into law enforcement databases. Detectives later learned that following his release from prison, Bolanos was deported to El Salvador in 1994.
Violent Crimes detectives then began working with the U.S. Department of Justice, Department of Homeland Security, and the Federal Bureau of Investigation to determine Bolanos’s whereabouts. Investigators found no record that he had ever returned to the United States after his deportation. Bolanos had originally entered the country on a work visa in the early 1980s. Authorities in El Salvador ultimately located him living near the same village he had listed on his original visa application.
Violent Crimes detectives presented the case to the Sonoma County District Attorney’s Office, and an arrest warrant for murder was issued to Bolanos. Sonoma County Detectives then began working with federal authorities and the Salvadoran government to have Bolanos arrested and extradited back to the United States to stand trial.
As federal authorities were preparing to take Bolanos into custody, he was found deceased inside his home in El Salvador. Investigators learned he had reportedly been battling cancer and appeared to have died of natural causes.
Although Bolanos will not face prosecution in court, the Sonoma County Sheriff’s Office has concluded that the evidence establishes he sexually assaulted and murdered Robert Pangborn.
The Sonoma County Sheriff’s Office remains committed to investigating cold case homicides. Each year, the Sheriff’s Office allocates $50,000 for DNA testing related to unsolved homicide investigations and has created a detective position that exclusively investigates cold case homicides. The agency currently has approximately 70 open cold case investigations dating back as far as 1967. Cases are constantly re-evaluated and all new leads investigated. We are continually attempting to seek justice for the victims and their families.
The Sonoma County Sheriff’s Office would like to extend our sincerest appreciation to the Sonoma County District Attorney’s Office, the Santa Clara County Crime Laboratory, the Serological Research Institute, the U.S. Department of Justice, the Department of Homeland Security, the Federal Bureau of Investigation, and all partner agencies whose professionalism and persistence were instrumental in resolving this case.
