Serial killer John Wayne Gacy's 19th victim was identified after more than three decades through the help of DNA evidence.

Investigators identified William Bill George Bundy as Victim 19, according Cook County Sheriff Tom Dart. The Cook County Sheriff's Department announced a second effort in identifying the remaining Gacy victims, Bundy's being the first successful use of DNA in that push. 

Bundy, a construction worker like many of Gacy's other victims, went missing before his 19th birthday in October 1976. His remains were found two years later in the serial killer's Chicago home.

Gacy brought many of his victims to his house by promising construction work. When investigators nabbed Gacy in 1978, they discovered 27 bodies inside his home, and six more in his backyard. He was convicted two years after his arrest, and finally executed in 1994.

Bundy fell into a category of anonymity among seven other Gacy victims. DNA techniques have progressed to a level where samples pulled from the remains and potential family members can be used to ID once-unnamed victims.

The forensic work in the late 1970s used dental records to identify bodies, which Bundy lacked. His brother and younger sister Laura O'Leary provided cold-case investigators with classic cotton-swab-to-cheek samples, which proved a match.

I always knew he was going to be one of them, O'Leary said at a press conference. But there was no DNA [testing] back then, so there was nothing I could really do.

Dart's office is open to accepting samples from others who believe their family members may be among the now-seven unidentified victims.