Authorities have identified a Pennsylvania teenager nearly 26 years after her murder in a rare case where investigators knew the killer's identity long before they knew the victim's name.The FBI's Boston field office, Massachusetts State Police and Suffolk County District Attorney's Office announced Wednesday that "Chelsea Jane Doe" has been identified as Tiffany Bradley, a 16-year-old from Allentown, Pennsylvania, through advanced DNA testing and investigative genetic genealogy.Bradley's killer, Eugene McCollom, pleaded guilty years ago and is serving a life sentence. But despite securing a conviction, investigators spent decades trying to determine the identity of the teenage victim."We have waited so long for this day," Massachusetts State Police Col. Geoffrey Noble said during a news conference. "It is rare to have a case like this one, where we knew the suspect's name before the victim's."HEADLESS, HANDLESS BODY FOUND ON NEW YORK ROAD 56 YEARS AGO IDENTIFIED THROUGH DNA, KILLER REMAINS UNKNOWNPolice discovered Bradley's remains on Nov. 13, 2000, in the parking lot of the Soldier's Home in Chelsea, Massachusetts, about 315 miles from her hometown.At Wednesday's news conference, Suffolk County District Attorney Kevin Hayden described the scene investigators encountered."They found a body of an unknown female," Hayden said. "Tragically, she had been cut in half. She was without her head and without any hands."COLD-CASE FUGITIVE BUSTED SOUTH OF THE BORDER AS NEW DNA TECH ALLEGEDLY TIES HIM TO TEENS ROADSIDE KILLINGAuthorities said McCollom, who remains incarcerated, admitted to killing Bradley after she arrived in the Boston area and later told investigators where additional remains had been buried.According to the FBI, Bradley had been trafficked across state lines before her death.Authorities said advances in DNA technology and genealogical research ultimately allowed investigators to identify Bradley and notify her family nearly 26 years after her death.DNA INNOVATION CREDITED IN IDAHO, RACHEL MORIN CASES SIGNALS SHIFT IN RACE TO CATCH KILLERS, LAB FOUNDER SAYS"Today, we can finally state her name: Tiffany Bradley of Allentown, Pennsylvania," the FBI Boston office wrote in a Facebook post announcing the breakthrough.For Bradley's family, the identification brought an end to decades of unanswered questions."Her last conversation with her favorite cousin was cut short with her voice trembling, saying, 'I'll call you later. I have to go,'" Bradley's relative, Shakirah Wiggins, said during the news conference. "That call never came and was replaced with 26 years of waiting, wondering why."Wiggins thanked investigators for continuing to pursue the case long after the killer had been identified."It is totally amazing that, after 26 years, people cared enough to give her a name and return her to our family," she said. "The wheels of justice run slowly, but surely."Fox News Digital reached out to the FBI's Boston field office for additional comment but did not immediately receive a response.