Pamela Butler. (Family photo/TV One)

More than eight years after Pamela Butler disappeared from her D.C. home, her onetime boyfriend has admitted that he strangled her, disposed of her body and tried to hide evidence at the crime scene.

Jose Angel Rodriguez-Cruz, 52, pleaded guilty Friday to second-degree murder and was sentenced to 12 years in prison. For the plea agreement to be finalized, he must lead authorities to the area where he hid Butler’s body.

Butler’s family members, who had long suspected Rodriguez-Cruz was the killer, said they are now focused on recovering their loved one’s remains.

“If he doesn’t get any time, we’re fine with that — we just want the body,” said Butler’s brother Derrick, 54.

Outside the courtroom, Butler’s 85-year-old mother, Thelma, said that she was “trying to remain strong” and that the plea agreement was “just a start.”

Thelma Butler and her son, Derrick Butler, in Thelma's Washington home in 2009. (Sarah L. Voisin/The Washington Post)

“We just want to give her a proper burial so we can put some closure to this,” she said.

D.C. Superior Court Judge Hiram Puig-Lugo reminded Rodriguez-Cruz that if he does not show a good-faith effort in helping authorities locate Butler’s remains, the agreement would be voided. If that happened, Rodriguez-Cruz would face a charge of first-degree murder.

Butler, a 47-year-old computer analyst for the Environmental Protection Agency, disappeared from her Northwest Washington home the day before Valentine’s Day in 2009. Security cameras had captured images of her and Rodriguez-Cruz shortly before she went missing, and he quickly became the main suspect.

But it was not until this year that police had the evidence to make an arrest, based partly on what authorities said was Rodriguez-Cruz’s history of violence toward women. D.C. authorities have said in court documents that his former wife, Marta Rodriguez, went missing in 1989 in Arlington and has never been found.

In court Friday, Assistant U.S. Attorney Deborah Sines said Rodriguez-Cruz described for authorities the final moments of Butler’s life, bringing some answers to the long-enduring mystery of what happened in the victim’s home that February.

Rodriguez-Cruz said he and Butler got into a fight in her home on Feb. 13, 2009, arguing over his lack of a job, according to the prosecutor. He said he punched Butler in the face and she fell to the floor. Then Rodriguez-Cruz climbed atop her and strangled her.

The following morning, Rodriguez-Cruz said, he turned the motion-sensor lights off outside the house and dropped Butler’s body out a first-floor window. He moved the body to his car and disposed of it before returning to the home to get rid of her phone and taking some other items.

Puig-Lugo asked Rodriguez-Cruz whether the prosecutor’s account was correct.

“Yes,” Rodriguez-Cruz said, standing next to his public defender.

In an interview with The Washington Post in 2009, when he was the prime suspect in the case, Rodriguez-Cruz denied harming Butler. He said the two had met through the online dating service eHarmony five months before she vanished.

A former military police officer, 5-foot-9 and stoutly built, Rodriguez-Cruz was living in Alexandria at the time and working as an office manager at a health clinic. In court Friday, Rodriguez-Cruz looked slight and haggard, a stark contrast to his appearance earlier this year.

Family and friends had described Butler as highly organized in her personal and professional life. Her home was always meticulously neat, and one of her colleagues at the EPA described her office as being “like Good Housekeeping.”

Butler also was conscious of her security, equipping her two-story house with an array of external surveillance cameras.

After she disappeared, relatives and police examined stored video from the cameras. Butler was seen arriving home on the night of Feb. 13. Rodriguez-Cruz was waiting outside for her, and the two entered the house together. At 9:48 p.m., Butler was seen again on the video, leaning out the front door to get her mail from the box.

The video showed Rodriguez-Cruz leaving the house about 11:30 p.m. But there was no video of Butler ever leaving.

After family members arrived at the house on Feb. 17, they noticed several small things amiss, including one that especially worried them: The blinds on a window leading to a side yard were open, and the window was unlocked. They said Butler would never have gone out leaving the window that way.

Butler’s disappearance and likely slaying remained a cold case for more than eight years, until a D.C. police homicide detective, Michael Fulton, took a closer look in February around the anniversary of Butler’s disappearance.

According court documents, Fulton located a witness who revealed new details about Rodriguez-Cruz.

The witness said that he had once seen Rodriguez-Cruz hold a gun to the head of a woman to whom he had been married as she begged for her life. The witness added that 22 years ago, he had found a letter that Rodriguez-Cruz wrote, admitting he was “responsible” for the disappearance of that woman. Fulton was suddenly searching not for one missing woman but two.

The witness who found the letter told police that he returned it to Rodriguez-Cruz “and never saw it again.” According to the affidavit, it read in part, “I Jose Angel Rodriguez Cruz am responsible for Marta’s disappearance.”

Marta Rodriguez, Rodriguez-Cruz’s wife, was a 26-year-old nurse aide living in Arlington County when she vanished in 1989.

No one has been charged in Rodriguez’s disappearance. Deputy Chief Daniel J. Murray of the Arlington police on Friday said there is an active missing-person case being handled by the cold-case squad.

Police had cleared the case in 2001 because authorities in Florida found a person who they then believed was Rodriguez living in the state. But this year, when the Butler case was reopened, detectives learned that the woman living under than name was actually an associate of Rodriguez-Cruz falsely using his wife’s identity.

Sines said Rodriguez-Cruz is expected to be released briefly from jail to meet with D.C. homicide detectives to direct them to Butler’s remains.

Derrick Butler said his family has experienced years of tumult as they searched for his missing sister and then finally had her legally declared dead. He said his mother has long kept an empty urn for cremated remains at her house, waiting for her daughter’s ashes.

Derrick Butler said the years since his sister vanished have been “agonizing.”

“Up and down. I mean, emotions all over the place,” he said. “From one moment to the next, you never know how you’re going to feel. And I’m just glad we’re coming to the end of it now.”

Rachel Weiner contributed to this report.