Several police departments in Texas plan to comb through hundreds of old cases involving the unattended or unexplained deaths of older adults to determine whether a healthcare worker charged with an attack at a senior living community and the murder of an elderly woman elsewhere could be responsible for other deaths.

Billy Kipkorir Chemirmir, arrested on capital murder charges March 20 in Dallas, also is suspected in the October attack on a resident at Parkview in Frisco, a Watermark Retirement Community offering independent living, assisted living and memory care in Frisco, TX.

Chemirmir, who has a criminal record, posed as a maintenance worker to try to gain entry to the resident’s apartment, Plano Police Chief Gregory W. Rushin alleged at a Friday press conference. After forcing his way into the apartment, Chemirmir knocked the woman off her walker and to the floor, put a pillow over her face until she passed out and then took her jewelry, Rushin alleged.

The resident survived. Chemirmir is accused of attempted capital murder in the case.

Watermark told a Texas television station that Chemirmir never had worked at Parkview.

“In late 2017, we reported this individual to the authorities for an intrusion into our community. We are thankful he has been apprehended,” the company said in a statement to WFAA. “We are cooperating fully with the authorities to assist them in any way possible. We are deeply saddened by the actions of this individual, and our hearts go out to the affected communities, their residents and family members.”

Chemirmir is a former healthcare worker “and has a history of impersonating maintenance personnel at a retirement community in Dallas,” Rushin said, although he could not provide details on his work history because the investigation is in the early stages. Tuesday, Plano police said Chemirmir may have used the name Benjamin Koitaba while working in healthcare.

It was under that name that Chemirmir allegedly falsely identified himself as an employee when he was arrested in March 2016 and June 2016 at Edgemere, a Senior Quality Lifestyles Corp. life plan community in Dallas, according to the arrest warrant from Frisco cited by the Plano Star Courier. He subsequently was charged with criminal trespassing and false identification as a fugitive. Chemirmir also was arrested for assault in 2012 and DWI in 2010, according to a Dallas criminal background check, the Star Courier reported.

Chemirmir may have “used his healthcare experience to his advantage in targeting and exploiting seniors,” Rushin said. “When you work in the healthcare industry working with seniors, you get an idea of the investigation that might occur whenever a death occurs, so I think he probably used that information to further his efforts in these crimes,” he said.

Frisco police identified Chemirmir as a suspect after he was arrested in Dallas for the murder of an 81-year-old woman discovered dead in her home when police conducted a welfare check. “Evidence at the scene indicated the victim may have been suffocated with a pillow,” Rushin said.

The welfare check had been done at the request of the Plano, TX, police, who were conducting surveillance of Chemirmir because he was a suspect in an attack on a 91-year-old woman at a seniors housing complex in their city that was similar to the attack in Frisco; that victim also survived. While watching Chemirmir, they allegedly saw him throw a jewelry box into a dumpster; that jewelry box belonged to the Dallas woman.

Now police in Dallas, Frisco, Plano and Richardson, TX, are investigating Chemirmir’s potential involvement in additional attacks and deaths in their cities.

David Pughes, executive assistant chief of police for the Dallas Police Department, said that based on the pattern that is emerging, his department will investigate unattended and unexplained deaths of older women dating back to 2010, the first year Chemirmir appears in the city’s criminal records database.

“In Dallas alone, our initial estimate is over 750 elderly females that we’re going to go back and review cases on,” he said. The department will work with various agencies, including the medical examiner, and may bring in the FBI, Pughes said.

Preston Place, a Plano retirement community where management recently was assumed by Solvere Senior Living, is “looking at recent deaths involving elderly women who had items stolen from their rooms,” WFAA reported.

The company told the TV station that, in addition to working with police, it “implemented a significant overhaul of the community’s security equipment and protocols” that included installing cameras, changing gate codes, reprogramming key fobs, implementing a background check program for third-party vendors, and issuing new uniforms and name badges for employees.