The suspect in a quintuple homicide in Oregon allegedly gunned down his girlfriend and her family, shooting all five victims multiple times before dying by suicide, authorities said.

Benjamin Parker, 36, is believed to have carried out the killings on Saturday morning at a rural property he shared near Forest Grove, according to the Washington County Sheriff's Office. The victims were identified as Parker's girlfriend, Stella Kimsey, 26; her grandmother, Mary Kimsey, 85; her mother, Rowan Kimsey, 60; Stella Kimsey's best friend, Linsey Haraldsen, 26; and Haraldsen's partner, Alvin Chu, 27.

Two dogs and two cats were also found shot to death at the scene. A third cat was wounded and later euthanized, Detective Mark Povolny said Tuesday at a news conference. Povolny added that Parker allegedly attempted to set fires at the bodies and the home.

Parker was later found dead in his car in Enumclaw, Washington, from an apparent self-inflicted gunshot wound, the sheriff's office stated. His mother told investigators that Parker called her Saturday night and confessed to the crime, Povolny said.

"He said he had been planning this for awhile," Povolny said of the suspect's reported confession. "He said he planned to kill three people, but two more people were also killed."

While Parker did not provide a motive to his mother, information gathered by investigators suggests a recent dispute between Parker and Stella Kimsey. Mary Kimsey had texted a friend on Friday night that Parker and her granddaughter had gotten into a "horrible fight" and that Stella had told him he needed to leave.

Haraldsen had reportedly been on the phone with Stella Kimsey around the time of the fight when the call abruptly ended, Povolny said. Haraldsen then attempted to contact Stella Kimsey's mother, Rowan Kimsey, who said she would check on her daughter. Rowan Kimsey never called back, prompting Haraldsen to travel to the property herself. When Mary Kimsey could not reach the three women, she planned to pick up Alvin Chu and go to the property.

"Although the suspect is deceased, this does not mark the end of our work," Sheriff Caprice Massey stated. "Our commitment now is to provide the families of Mary, Rowan, Stella, Linsey and Alvin with answers as we learn them. They deserve nothing less."