In a YouTube video posted several months ago, Rita Sanders-Campfield spoke about losing her husband to pancreatic cancer and a deepening depression that led to a year-long hospitalization.

“It took a lot of work to get myself to a better place,” she said, noting that one big sign of progress was her ability to move out of her mother’s home and, eventually, into a shared apartment in Montgomery County. “Luck isn’t what matters. It is perseverance. Today, I live in a lovely, beautiful home in North Bethesda with my roommate Chong Park.”

But for reasons not clear, Sanders-Campfield, 53, attacked Park, 67, inside their apartment, fatally stabbing her with a butcher knife and a pair of scissors, police said Wednesday.

Mental illness may have played a role, officials said.

Detectives discovered that Sanders-Campfield, who has a zoology degree from Duke University, had kept a handwritten journal, and they said they spotted an entry in which she wrote that she thought Park was evil and practiced witchcraft. During a hearing Wednesday in Montgomery County District Court, an official at the county jail said Sanders-Campfield “seemed to be in a catatonic state.”

Rita Sanders-Campfield (Montgomery County Police)

Park and Sanders-Campfield appeared to have been brought together by a nonprofit organization called Housing Unlimited, based in Silver Spring, which helps low-income people in mental health recovery find permanent homes.

Abe Schuchman, the group’s chief executive, said Park had been a tenant since 2006, and that he and his colleagues were deeply saddened by her death.

“During these eight and a half years, she was a model tenant — caring, conscientious, warm, friendly, and well-liked by all,” Schuchman said in a statement.

The statement did not mention Sanders-Campfield, and officials did not say whether she had been assisted by the group. But Sanders-Campfield said in her video, which was posted on YouTube by Housing Unlimited in June, that the group helped her find housing.

“Housing Unlimited has served hundreds of individuals over the years,” Schuchman added. “The death of Ms. Park is the only incident of this nature in our 20 years of operation. Again, our hearts and prayers are with the Park family.”

Efforts to speak with family members of the suspect and victim were not successful.

The case follows a series of killings in Montgomery overlaid with mental illness.

“Initial reports seem to indicate that, yet again, there is a mental health aspect to this most recent homicide. This continues a disturbing pattern,” said John McCarthy, the county’s top prosector. “The intersection of mental health and the criminal justice system has never been more evident than it is today, and we must respond to this challenge.”

Detectives are investigating the possibility that Park was killed several days before her body was discovered Tuesday.

In the YouTube video, Sanders-Campfield talked about the struggles in her life and how things seemed to be getting better.

Sanders-Campfield said that in 1999, her husband died soon after he was diagnosed with cancer. “It happened so quickly. I was in a bad place. I didn’t think that I could continue to live in the same home without him. I was fortunate that my mom allowed my son and I to move in with her,” she said.

She fell into a depression, spent more than a year in a hospital, and ultimately set out to find a place of her own. She found Housing Unlimited, which helped get her in the apartment along Old Georgetown Road, near Rockville Pike, about two miles north of the Capital Beltway.

“Our two-bedroom condo is perfect for both of us,” Sanders-Campfield said in the video. “It has a party room, a gym, a grocery store across the street, and it’s right near the Metro.”

Sanders-Campfield spoke with pride about her children — 24 and 26 — and how she was about to fly to Missouri to see her son graduate with a master’s degree in engineering. She spoke excitedly about working as a teacher.

“I am excited by the possibilities that are out there,” she said, speaking clearly with a smile.

But by last week, things seemed to have changed. On Friday, Park’s daughter was in town and spoke with her mother and with Sanders-Campfield, according to court records.

Sanders-Campfield talked to the mother and daughter about religion, and how she was seeking to be “perfected.” When Park’s daughter asked Sanders-Campfield how she was doing, Sanders-Campfield said “she was not doing well,” according to charging documents.

Park’s daughter, who appears to live in Upstate New York, couldn’t reach her mother the next day, a Saturday, and couldn’t reach her afterward, either. At some point, she requested that Housing Unlimited check on her mother. On Tuesday morning, a person from the nonprofit group knocked on the apartment door, got no response and used a master key to get inside, according to charging documents. He saw Park’s body on the bedroom floor, backed out and called police.

Shortly after 10 a.m., officers who arrived found Park with a butcher knife in her back. They found a bloody pair of scissors on Park’s bed.

Sanders-Campfield was in the apartment, “moving on her bed,” according to police. She had injuries to her right arm.

“Possibly bite marks,” detectives wrote in arrest records.

During the Wednesday court hearing, a staff member at the Montgomery County jail told the judge that Sanders-Campfield couldn’t complete a discussion with a therapist. A public defender also said in court that she had tried to talk to Sanders-Campfield at the jail Wednesday morning but that the defendant was unable to have a conversation.

District Judge James B. Sarsfield ordered Sanders-Campfield to be held in jail and undergo a mental health evaluation. She is set to return to court Wednesday for a bond review.

Magda Jean-Louis and Julie Zauzmer contributed to this report.