The pieces of the puzzle.
In the early 2000s, investigators were able to obtain DNA from the unknown killer from the 1980 double murder in Ventura County, California.
Investigators plugged the mystery killer's DNA into a genealogy database. Based on the pool of people on the genealogy website, investigators were then able to build a family tree of the unknown killer’s relatives. They narrowed the search based on age, location and other characteristics, eventually leading them to DeAngelo.
Authorities surveilled DeAngelo and collected his discarded DNA. Investigators plugged his discarded DNA back into the genealogy database and found a match, linking DeAngelo's DNA to the DNA gathered at multiple crime scenes.
DeAngelo was taken into custody at his home in Sacramento County, the same county where his alleged 10-year crime spree began. [ABC].