OREGON – A few months ago, as he was serving a life sentence for killing his cellmate in an Oregon prison, Thomas Riffenburg got what he would later describe as a "smack on the head from God."
Riffenburg said God was telling him what he did was wrong, he told authorities.
But the divine intervention was not about the case in which he'd stomped a fellow inmate to death.
It was about something else: The disappearance of his girlfriend and baby boy, who had not been heard from since they were reported missing in 2009.
Riffenburg, 31, wrote a letter to a special agent with the Oregon Department of Justice.
He offered to provide her with "dates, times and location of the missing persons."
When the two met face-to-face in June, Riffenburg handed the agent a pair of hand-drawn maps, each revealing a grave.
"I did it," Riffenburg said, according to court documents obtained exclusively by CNN. "They both suffocated to death."
Riffenburg's confession, recounted in a search warrant affidavit filed in Los Angeles Superior Court, would provide answers to loved ones who had been wondering for eight years about the fates of Jennifer Anne Walsh and her 16-month old son, Alexander.
But the details of his revelation would bring the family a new kind of torment as well.
The following account is based on court affidavits filed by LAPD homicide detectives working on the case, and an interview with a family member of the missing woman and child.
'A better life'
On the morning of January 11, 2009, Joanne Fern walked into a Los Angeles police station to report her daughter, Jennifer Anne Walsh, missing.
Walsh, 23, was a petite blonde — she stood just 4 feet 11 inches — with a pierced nose and a tattoo of a marijuana leaf on her back. She had a soft spot for those in need, her mother would later recall.
Fern told the officer who took the report that Walsh had last been seen by her boyfriend, Riffenburg, who had driven her to an unemployment office in Los Angeles' San Fernando Valley.
Fern provided the officer the account she said Riffenburg had given her: Walsh had been caught with a bag of marijuana inside the office. Fearing the drug possession could lead authorities to take her child, she hurried out to her boyfriend, who was waiting in her van, and told him to drive away with the boy.
Riffenburg brought Alexander to Fern's house in the L.A. suburb of Palmdale, about an hour north of the city, she told the officer.
Fern waited nearly three days — the amount of time she believed was required to file a missing persons report — before driving to the police station. She told the officer who took the report that she had not had any contact with her daughter since Riffenburg last saw her at the unemployment office.
When Fern returned home from filing the report, Riffenburg and her grandson were no longer there. She found that her safe had been opened and money and jewelry were missing.
There was also a note from Riffenburg, stating "he and Jennifer were leaving for a better life."
Fern called another daughter, Christina West, and learned that Riffenburg, Jennifer and Alexander had been staying with West at her house in the Palm Springs area until recently. West had asked them to leave because the house was small and Riffenburg was refusing to look for work, she would later tell authorities. West received a text early one morning sent from her sister's phone saying all three had left.
The family heard nothing until a year later when they belatedly learned that Riffenburg had been arrested for burglary in Oregon the month after Jennifer and Alexander were reported missing.
Riffenburg told the detective handling his case that his girlfriend and son had been killed in a traffic accident. The detective did not learn the details of the purported accident or link Riffenburg to the missing persons case involving his girlfriend and son.
In December 2010, an LAPD detective following up on the missing persons report asked the Oregon State Police to conduct a follow-up interview with Riffenburg.
Riffenburg admitted that he'd stolen money from Joanne Fern's safe and left the note in 2009 saying he and Jennifer were leaving for a better life. He said Jennifer and Alexander were living in California. He knew their address, he said, but would not divulge it, because "he did not want her parents involved in her life again." He offered to write Jennifer a letter and have her contact the police.
Between 2009 and 2015, while living in Oregon, Riffenburg was arrested several times for "serious offenses ranging from burglary to murder," according to court records.
He was in prison in June 2013 when guards found his cellmate at the Snake River Correctional Institution unconscious and severely beaten. The man died several days later.
Two years later Riffenburg pleaded guilty to aggravated murder and received a life sentence.
Nearly two more years would pass before he wrote to Jodi Shimanek, the special agent with the Oregon Department of Justice.
Shimanek asked Riffenburg the obvious question: Why did you do it?
He told her he had made a promise to people he'd previously done time behind bars with, whom he considered "his family," that "they would always come first."
He could not keep that promise, he explained, "with Jennifer and Alexander in the picture."
He gave the agent a pair of hand-drawn maps, marking the grave sites where he said he buried Jennifer wrapped in a blanket and Alexander wrapped in plastic.
Jennifer's grave was in her sister's backyard; Alexander's was behind Fern's house.
Authorities recently obtained search warrants to dig up the remains.
In a recent interview with CNN, Fern said authorities found human remains believed to be her daughter's, but are awaiting the results of DNA testing for confirmation.
She said investigators have been unable to find Alexander's remains on the 14-acre property where she and her husband lived at the time her daughter and grandson disappeared.
Fern said that, in addition to his confession to police, Riffenburg confessed to her in a letter she received in July. She provided a copy to CNN.
"Joanne, what do I say to you?" the letter began.
"I told the authorities on 6-20-17 that I killed both of them, and I told them where to find the bodies," Riffenburg wrote in the letter dated June 28.
He added, "I don't expect any of you to forgive me, I wouldn't, and don't."
Riffenburg alluded to the killing of his cellmate and said, "something happened to me" when he did it.
"If you want the full story I will tell you, just let me know," he wrote.
"When I go to court for this, I will simply tell them that I am guilty, and offer no excuses," Riffenburg wrote. "I'm sorry, for what I did to them, and what I did you."
Fern wrote him back earlier this month, she said. She shared a copy of that letter with reporters as well.
She told him she was in shock over his confession, and asked for answers to "how you could do something so bad?"
"I knew you were troubled," Fern wrote. "But how troubled I didn't know."
In the interview, Fern said she has since learned that Riffenburg spent years in a juvenile facility for a violent offense before meeting Jennifer. CNN has been unable to independently verify that information because juvenile records in California are not public.
She asked Riffenburg in her letter why he didn't murder her and her husband as well.
"You had three days with us," she wrote.
Fern told Riffenburg she did not want him to be put to death for killing her daughter and grandson.
"You will live your life with this burden until the end days when God will see that it is your time to go meet him and he will decide your fate," she wrote.
She added, "even you can go to heaven if you repent and atone for the sins you did here on Earth."
But her letter was also a request for help. In it, she sent Riffenburg an old Google Earth photo of her property taken from around the time of the disappearances.
"Can you show on the map of our old place where you buried Alexander?" she wrote. "They have been looking for him but cannot find him."
Also included in the letter were some photographs of Jennifer and Alexander. In one, taken when Alexander was a newborn, his tiny head rests in Riffenburg's palm as he kisses the boy's forehead.
"I don't know how he'll be able to look at these," Fern said, as she showed copies of the photos to reporters.
"I hope they're like a knife to his heart," she said, twisting an imaginary weapon in her hand as she spoke.