The San Bernardino County Sheriff’s Department, headed by  led by Sheriff Floyd Tidwell, conducted the investigation of the Chino Hills Murders.

The following is a daily account of the murder investigation from the time it was discovered until Kevin Cooper was charged with the murders. These accounts are taken from court documents and newspaper articles.

Sunday June 5th 1983

  • Murders are discovered around 11AM. Survivor, Joshua Ryen is airlifted to hospital.
  • A neighbor reported to investigators about seeing 3 white or hispanic men drive away from the Ryen’s house Saturday afternoon.
  • Police search for three recent escapees from CIM as possible suspects; Alboro Knori, David Troutman, and Michael Martinez.
  • Tidwell tells media there is “no indication that either the escapers or the visitors were involved.”
  • A hatchet is found by the side of an adjacent road leading away from the Ryen’s house. Testing on the hatchet is botched, rendering all forensic evidence useless.
  • Loaded weapons belonging to the Ryens are found in the bedroom close to the victims bodies.

Monday June 6th 1983

  • 60 people would be allowed at the murder scene over the next two days – with up to 14 detectives in the Ryen’s bedroom at the same time.
  • Escapee, Alboro Knori is captured in Temple City, 40 Miles from the crime scene
  • Sheriff Tidwell holds a news conference and says investigators believe the deaths occurred in rapid succession and that more than one assailant was involved.

Tuesday June 7th 1983

  • A Crime Bulletin was issued for 3 White or Hispanic males in connection with the murders.
  • The Sheriff’s department discovers that escapee Daivd Trautman is actually Kevin Cooper.
  • Sheriff Tidwell holds a news conference telling reporters that in a vacant house, less than 100 yards away , “had evidence in it that leads us to believe the person that was in that home perpetrated the murders of the Ryen family.”, and that “We found blood in the residence, smears of blood, some clothes that had been left there and some other items of evidence I’m not a liberty to reveal.”
  • Fingerprints from the vacant house are found to be Kevin Cooper’s
  • District Attorney Dennis Kottmeier orders the crime scene dismantled. The carpet is pulled up, large sections of the sheet-rock walls are cut out with an electric saw. Over the next two days all doors and furniture had been moved to a warehouse. Extreme temperatures in the warehouse rendered all forensic testing useless.

Wednesday June 8th 1983

  • Escapee Alboro Knori is questioned and cleared of any connection to the murders.

Thursday June  9th 1983

  • Escapee Michael Martinez is questioned and cleared of any connection to the murders.
  • Sheriff Tidwell holds a press conference to announce that Kevin Cooper had been charged with four counts of murder and one count of attempted murder. He told reporters that there is proof Cooper was at the scene of the murders and “At this time we believe he is the only one involved.”