A home health aide accused of killing an 81-year-old woman in Texas is now suspected in the deaths of 11 other women by smothering them with a pillow before robbing them, court records show.

Accused serial killer Billy Chemirmir, 46, was indicted Tuesday on five additional counts of capital murder in Collin County and six counts in Dallas County, where authorities believe he snuffed out the lives of women in their 80 and 90s dating back to May 2016, the Dallas Morning News reports.

Chemirmir, a Kenyan citizen who was living in the U.S. illegally, has been jailed since March 2018 in connection with the death of Lu Thi Harris, a North Dallas woman who was found suffocated in her bed.

Investigators zeroed in on the home health aide after a 91-year-old woman told police in Plano that a man put a pillow over her face until she passed out and stole jewelry from her apartment.

Chemirmir was later spotted by police dumping a jewelry box into a trash bin, which ultimately led investigators to Harris’ home, where she was found dead.

Chemirmir is also facing two counts of attempted murder in Collin County, where authorities say he tried to smother two other women.

Investigators said in March 2018 that they were combing through up to 750 unsolved deaths to see if Chemirmir was linked to the cases. He had been living in the Dallas area since at least 2010, police said.

“We’re worried we could have more,” Dallas Executive Assistant Chief of Police David Pughes said last year. “It will be a monumental task. But we’re up for the challenge and we’re gonna make sure we check each and every case.”

Chemirmir’s bond as of Thursday was set at $9.1 million. He’s also facing an immigration hold, jail records show.

An attorney for the mother of one of Chemirmir’s suspected victims, 92-year-old Doris Gleason, said the woman was smothered inside her apartment at a senior living center in Dallas in October 2016.

Chemirmir gained access to the residence while posing as a maintenance worker but slipped past lax security at the facility, attorney Richard Arnold told KXAS.

“We certainly think he should have been noticed on the day Doris Gleason was murdered,” Arnold told the station.