The three women and a teenage girl were stabbed to death between 1978 and 1981 in the Denver area. Police did not divulge information about the cases Friday, but Denver Police Commander Matt Clark said there was an "underlying sexual component."
Police recently used DNA evidence to identify the killer as Joe Ervin, who took his own life 41 years ago after being arrested for the fatal shooting of an Aurora police officer.
Authorities exhumed Ervin's remains in late 2021 and found his DNA matched that found at the crime scenes.
"While the perpetrator cannot fully be held accountable for his despicable actions, we hope that knowing who is responsible can bring some peace to the families," Denver Police Chief Paul Pazen said Friday at a news conference.
The killings had initially been investigated as separate cases. The deaths were tied together between 2013 and 2018 through DNA evidence. In 2019, the Denver Police Crime Laboratory learned of a "positive ancestry link" in Texas.
Two years later, authorities, while doing a search in Texas records for biological relatives of the killer's DNA profile, got a match of someone close to the then unidentified suspect.
Eventually, Ervin was identified as the possible killer and his remains were exhumed. Earlier this month, DNA analysis confirmed Ervin was the killer, police said.
The victims were Dolores Barajas, 53; Madeleine Furey-Livaudais, 33; Gwendolyn Harris, 27; and Antoinette Parks, 17. Police did not release a photo of Barajas at her family's request.
"We can finally have peace knowing who did this to my little sister," said George Journey, one of Parks' brothers. "I'd like you guys to know, we have closure."
He said his mother and three other sisters had died in the years since the killing, and he wished they were there to know the killer had been identified.
Parks was six to seven months pregnant, and a high school student, when she was killed.
"It's been a lot of information to absorb so suddenly after all this time," said Molly Livaudais, who was a young girl when her mother was killed.
She lauded the officer who Ervin fatally shot.
"With her sacrifice she prevented him from killing anyone else, and it's clear that he was not going to stop on his own," Livaudais said, describing her mother as a writer and ecologist who had a very bright future.
Ervin killed Aurora police officer Debra Sue Corr, who was shot with her gun while handcuffing Ervin after a traffic stop. Ervin then shot a bystander who tried to help the officer, police said.
Police did not comment on other cases Ervin might have been involved with, but Livaudais said she learned he "assaulted an uncounted number of others."