DALLAS (CBSDFW.COM) – Police reports, civil lawsuits, and other court records dating back to 2016 reveal investigators suspect alleged serial killer Billy Chemirmir committed at least 24 murders throughout Dallas and Collin counties.

Together they paint a picture of man who targeting one senior living community at a time, moving to the next whenever it seemed he might get caught.

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Police began to piece together the story on March 19, 2018, after firefighters revived 91-year-old Mary Bartel.

According to a police report, Bartel told them a stranger forced his way in, grabbed a couch pillow, and smothered her until she blacked out. Then, he walked out with her jewelry.

Just one day earlier and one door over, Mary’s next-door neighbor, Ann Conklin, had died.

Ann Conklin (Dallas County Court Records)

Plano Police suddenly started taking a closer look and discovered a pattern of deaths in their Preston Place senior living community. There were seven within a 6-month period in that complex.

All had jewelry missing.

Diane Delahunty was one of the victims at the complex, whose death had initially been assumed to be from natural causes.

“The mentality was, well, these are seniors. It’s all natural,” says her daughter Lori.

She believes the killer took advantage of the lapses in the complex’s security.

“I mean, he had access. He had free rein, and nobody was stopping him,” said Lori.

A week before Mary Bartel’s attack, a neighbor happened to notice noticed a silver Nissan Altima that seemed out of place.

He jotted down its license plate and when police started asking questions, he passed it along. Investigators found it belonged to a man named Billy Chemirmir.

Billy Kipkorir Chemirmir (credit: Dallas County Sheriff’s Department)

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Years earlier, in 2016, Chemirmir had been caught twice at the Edgemere senior living apartments in Dallas, using a fake name and falsely claiming to be an employee.

Police now believe by the time he was stopped and charged with trespassing there, he’d already killed three women in that complex – Catherine Sinclair, Phyllis Payne, and Phoebe Perry.

The next eight murders he’s linked to started the following month at the Tradition Prestonwood senior living facility. Among the victims were Leah Corken and Doris Gleason.

After Gleason’s death, there’s a yearlong gap before the murders pick up again in late 2017.

Cheryl Pangburn discovered her mother’s body at her Parkview apartment in Frisco.

“Her body was perfectly positioned between the couch and the coffee table,” she recalls.

One month later, a “93-year-old” reported a “well-dressed” man posing as a “maintenance worker” had asked her if she needed work done.

When she said no, he “knocked her from her walker” and tried to “muffle her screams and smother her” with a pillow. But she survived and would, months later, pick Chemirmir out of photo lineup.

After that, came the string of fatal attacks at Preston Place retirement community in Plano and a murder of an elderly woman in her own home.

Once police started looking Chemirmir, the pieces began coming together.

On March 20, 2018 – the day after the attack on Bartel – officers were staked out at Chemirmir’s apartment complex, when they say he arrived home and tossed something a dumpster.

Inside they found a jewelry box belonging to Lu Thi Harris.

In his car, they say, were the keys to her Dallas home, where officers later found her.

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A medical examiner determined that final victim died only about an hour before his arrest.