In a concerning string of events, a senior living community in Texas experienced a series of mysterious deaths before Mary Bartel, a 91-year-old resident, was discovered unconscious in her apartment.

“Ms. Bartel was expected at an exercise class that morning,” recounted Glen Fitzmartin, Assistant District Attorney of Dallas County, in the show Unknown Serial Killers of America from Oxygen. “When her neighbors came to fetch her, they knocked on her door, but received no reply.”

Mary Bartel, who had spent years as a teacher and was residing at Preston Place in Plano, Texas, was immediately taken to the hospital. In a remarkable turn of events, she regained consciousness and disclosed a chilling story.

According to Bartel, a man had knocked on her door and then proceeded to force her onto the bed, attempting to smother her with a pillow before making off with her jewelry.

“He pressed down so forcefully,” Bartel recalled from her hospital bed, “that I couldn’t do much else but lie there.”

Investigators suspected she was the sixth victim at the upscale senior living community who had been attacked by a calculated killer targeting vulnerable, older women.

Her chilling account helped lead police to Billy Chemirmir, a well-dressed man from Kenya who worked as a caregiver for the elderly.

Though Chemirmir was only convicted of two murders, he was indicted in connection to 22 deaths and was suspected of killing many more.

“He was an incredibly prolific killer,” one victim’s daughter Jennifer Bassett remarked. “How does such evil exist?”

Chemirmir was finally stopped, in part, due to Bartel’s bravery.

“She was the leader of the family and she was always so strong, someone who was born to a very poor farm family who ends up taking down a serial killer,” her son Rick Bartel remarked. “That’s a pretty good story.”

String of Deaths Begin at Preston Place

Preston Place was considered a tight-knit community where residents enjoyed the camaraderie of other seniors.

As investigator reporter Lise Olsen noted, “The reputation of these upscale, independent living places was that they are safe spaces.”

But on March 7, 2018, Plano Police launched an investigation after the family of the late Martha Williams reported that about $7,600 worth of jewelry had been stolen after her death, including a wedding ring that she never typically removed.

“I wanted to know more about the actual death investigation,” Plano Police detective Jennifer Chapman explained. “So I start looking at the report.”

Though the death was deemed an unattended natural death by the medical examiner’s office, Chapman noticed Williams had been found next to her bed and her shirt had been pulled up over her head under what she deemed “suspicious” circumstances.

As Chapman dug deeper, she learned that there had been three other unattended deaths at the facility since October 2017, all elderly women who appeared to have died from natural causes.

According to Fitzmartin, “These individuals were found either laying on a bed or laying on the ground right next to the bed.”

There were no signs of foul play or signs of a break in and the apartments were typically locked when the bodies were discovered.

“All of them lived by themselves, some had recently been widowed. These individuals were very active,” Fitzmartin explained. “And when they’re found deceased…it was shocking to the family.” 

Though no jewelry had been reported missing in the other cases, Chapman went back to speak to the families and learned that in all of the cases, family members did discover jewelry had been taken. 

“At that moment, we realized, oh boy,” she said. “These cases have got to be connected.”

Victim Miriam Nelson Provides Telling Clue Before Her Death

Investigators began to suspect that were dealing with a serial killer.

“Somebody who is repeatedly killing similar types of victims with the same MO,” criminal forensic psychologist Dr. Maris Mauro explained. “What seems most obvious is there was some type of money motivation. That’s very unique.” 

Meanwhile, Preston Place had another unattended death on March 9 when 81-year-old Miriam Nelson was found dead on her bed. Once again, about $11,000 in jewelry had been stolen. 

One of her family members remembered Nelson telling them two days before her death that someone posing as a maintenance person had come into her apartment and may have taken some of her jewelry.

She described the person as a well-dressed, bald, Black man. 

Fitzmartin explained, “The management company told police there was no one matching that description working at Preston Place.”

After putting out a description of the suspect to residents, a resident’s son spotted a man getting into his car who matched the description and jotted down his license plate number.

Police were able to link the car to 45-year-old Chemirmir.

More Victims Are Discovered as Police Hone in on Suspect Billy Chemirmir

According to Plano Police Detective Jon Hoffman authorities desperately wanted to speak to the man who had become their prime suspect.

“This is all hands on deck,” he said. “But at the same time we’re trying to find Billy Chemirmir, Plano Police department gets another 911 call.”

Bartel had been attacked in her apartment—but survived to tell the tale to police. From her hospital bed, she said a man matching Chemirmir’s description had forced his way inside.

“He just said, ‘Don’t fight me, just get on the bed,’” she remembered. “Of course, I had no idea what was going to happen next, but he grabbed a pillow off my bed and just forcibly pushed down very hard.”

She described not being able to breathe.

“I thought I would die,” she said, “which I’m not afraid to die, but I didn’t want to die that way.” 

When she regained consciousness at the hospital, she discovered her wedding ring and another diamond ring she had been wearing were missing.

Just hours after Bartel was attacked, as police were still processing her apartment, Jennifer discovered her 82-year-old mother Ann Conklin dead across the hall.

“My mother’s on the floor, face down,” she remembered, “and I can see that she isn’t moving and start screaming.”

Much like the other cases, her diamond necklace and watch were missing.

Billy Chemirmir is Arrested in Connection With Senior Living Deaths

As police were waiting for Chemirmir to return to his apartment, Hoffman found someone with an account linked to Chemirmir attempting to sell Bartel’s ring on the online site OfferUp.

Chemirmir was arrested and taken into custody on March 20 after he was spotted outside his apartment throwing a red jewelry box into the dumpster.

Inside the jewelry box, police found the name and address of a Lu Thi Harris, an 81-year-old living on her own in a Dallas home. 

Dallas Police were sent to do a welfare check and discovered Harris dead inside, laying next to her bed. A pillow smeared with her makeup lay nearby.

“I was in utter shock,” Chapman said. “Like, truly, he’s a monster.”

After finding a grocery receipt in her home from Walmart, detectives went to the store and saw a man matching Chemirmir’s description on surveillance footage following behind her, strengthening their case against him.

Hoffman explained, “He’s hunting when he’s doing this.”