The notorious "Golden State Killer" was behind serial rapes and murders across California in the 1970s and 1980s -- but decades passed before a suspect was identified.
In 2018, Joseph DeAngelo was arrested, and on June 29 the 74-year-old former police officer is set to plead guilty to a string of crimes.
Here's a look back at the case:
From 1973 to 1976, DeAngelo was a police officer in Exeter, California, officials said.
On Sept. 11, 1975, DeAngelo, while serving as an Exeter police officer, allegedly shot and killed professor Claude Snelling at his Visalia, California, home, according to Visalia police.
Visalia is 10 miles away from Exeter.
DeAngelo then served as a police officer in Auburn, California, from 1976 to 1979.
He was fired for allegedly stealing a hammer and a can of dog repellent, The Associated Press reported, citing Auburn Journal articles from the time.
In the summer of 1976, burglaries and rapes terrorized the eastern district of Sacramento County.
The "Golden State Killer" would break into his victims' homes by prying open a window or door while they slept, the FBI said.
Sometimes he would take jewelry, identification, cash and coins from the victims' homes.
In February 1978, the "Golden State Killer" shot and killed Brian and Katie Maggiore, who were walking their dog in the Sacramento area.
The burglaries continued in the East Bay area of Northern California, and then escalated into rapes and murders along the California coast, the FBI said.
According to the FBI, the "Golden State Killer" would often "attack couples, tie up both victims, rape the female, and then murder them."
On Dec. 30, 1979, Alexandria Manning and Robert Offerman were killed in Goleta, near Santa Barbara.
In March of 1980, Charlene and Lyman Smith were killed in Ventura, north of Los Angeles.
In August of 1980, Keith and Patrice Harrington were slain in their home in Dana Point in Southern California.
On Feb. 5, 1981, 28-year-old Manuela Witthuhn was raped and killed while home alone in Irvine in Southern California.
In July 1981, Cheri Domingo and Gregory Sanchez were killed in Goleta.
No crimes were attributed to the "Golden State Killer" from July 1981 until 1986, when 18-year-old Janelle Cruz was raped and murdered in Irvine.
That was his last known crime.
The case went cold for decades.
DeAngelo's name came up for the first time in the investigation in 2018, Sacramento District Attorney Anne Marie Schubert said.
DeAngelo became the first public arrest obtained through genetic genealogy, a new technique that takes the DNA of an unknown suspect left behind at a crime scene and identifies him or her by tracing a family tree through his or her family members, who voluntarily submit their DNA to public genealogy databases.
To identify DeAngelo, investigators narrowed the family tree search based on age, location and other characteristics.
Once authorities zeroed in on DeAngelo, they surveilled him and collected his DNA from a tissue left in a trash.
Investigators plugged his discarded DNA back into the genealogy database and found a match, linking DeAngelo's DNA to DNA found at crime scenes, prosecutors said.
He was arrested in April 2018 in Sacramento County.
Since DeAngelo's arrest, over 150 suspects have been identified through genetic genealogy.
DeAngelo is charged with 13 murders and multiple rapes and burglaries.
He is expected to take a plea deal on June 29 to avoid the death penalty, victims' relatives told ABC News.
Monday's court hearing will be held at a California State University–Sacramento ballroom. With over 150 victims and relatives expected to attend, prosecutors sought a room that would be large enough to accommodate them and promote social distancing, The Sacramento Bee reported.