For decades, the teenage girl whose remains were found, with those of her unborn child, along the Lehigh River in Carbon County in 1976 was known only as "Beth Doe." 

That is, until last week, when Pennsylvania State Police identified her, and arrested her alleged killer.

A Queens, New York man is now behind bars, charged with murdering his then-girlfriend, 15-year-old Evelyn Colon, and their unborn daughter, then disposing of the human remains in East Side borough.

The long-awaited answers stemmed from decades of investigation and one critical breakthrough--a DNA match with Evelyn's nephew, Luis Colon Jr.

"Is this really happening, is this really it?" 

Those were the questions racing through Colon Jr.'s head, as a detective told him the DNA he submitted online four years ago was a match for the girl who is buried under a "Beth Doe" grave in Carbon County.

"I always was curious and I wanted to see if I could get in touch with her or my cousin," said Colon Jr.

For decades, Luis, and the rest of the Colon family, thought his aunt, was a teenage runaway. She had been missing since the 1970's.

"I found it hard to believe growing up that she would abandon the family permanently," he said.

Last week, the family, along with the rest of the world, found out from Pennsylvania State Police that she, and her unborn baby girl, were instead the victims of a 1976 cold case murder.

"There's no happy ending in this story. The whole point of me doing the DNA was to connect with one of them, build a relationship, find out what happened," said Colon Jr.

Court documents say what happened is Evelyn's then 19-year-old boyfriend, Luis Sierra, allegedly strangled and shot the mother of his child. He then cut off her arms, legs, and ears, before stuffing the remains in three suitcases. They were found a day later along a river bank under the Interstate 80 bridge near White Haven. Authorities say the suitcases were thrown from the bridge to the ground below

"He murdered two children, a 15-year-old and a full-term baby," said Colon Jr.

Once in contact with the Colon family, investigators learned the girl was last seen in Jersey City, where she was living with Sierra.The couple had moved out of their apartment and Evelyn had told her mother Sierra was abusive. She said if anything ever happened to her, he was likely involved.

But the family never reported her missing.They received a letter saying she and the baby were doing well. Authorities now believe Sierra wrote that letter.

"There is no other person on this planet who has a motive to harm her besides him, it's clear as day," said Colon Jr.

The case sparked national interest over the last 44 years, leading to the creation of the "Carbon County Beth Doe" Facebook page. The "Beth Doe" story haunted followers like Stacy Solomon of western Pennsylvania, who was born December 20, 1976--the exact day Evelyn's remains were found.

"Knowing that her daughter would have probably been born on my birthday or shortly after my birthday so that was truly a haunting thing for me and I felt a deep connection to that," said Solomon.

Weatherly resident Bette Rambaran lives near the cemetery where Evelyn and her daughter, who the Colon family has named Emily, are buried. She and her family are some of the many who visit the grave from time to time.

"He picked probably what to him was a random place to throw her, and we put a lot of love around her," said Rambaran.

Authorities arrested the now 63-year-old Sierra last week in Ozone Park, New York. But they may have never found him, if not for the DNA match with Evelyn's nephew. Investigators say the Colon family led them to Sierra's Queens home.

"My goal in all this is to get the closure and the closure would be seeing him serve time and I am glad he is alive to face justice and to face us as a family and I'm looking forward to that day," said Colon Jr.

Sierra is in custody and still awaiting extradition to Carbon County. Meanwhile, Evelyn's family is raising money to move her and Emily's remains to another burial site.