A Dallas man previously arrested in the death of an 81-year-old woman has been charged with killing at least 11 more elderly women whose jewelry and other valuables he stole, authorities said Thursday.

Kim Leach, a spokeswoman for the Dallas County district attorney’s office, said 46-year-old Billy Chemirmir was indicted Tuesday on six more counts of capital murder in the deaths of women ranging in age from 76 to 94.

Chemirmir, a Kenyan citizen who was living in the U.S. illegally, also is charged in nearby Collin County with two counts of attempted capital murder for similar attacks there, according to county court records.

A Collin County grand jury also returned five capital murder indictments against Chemirmir on Tuesday.

Chemirmir has been in custody since March 2018 in the death of the 81-year-old Dallas woman, Lu Thi Harris. Police in Plano were investigating Chemirmir in connection with suspicious death and suspicious person calls at a senior apartment complex in that Dallas suburb and found evidence linking him to Harris’ death in Dallas, authorities said. Plano is in Collin County.

The break in the case came when Chemirmir forced his way into the Plano apartment of a 91-year-old woman that March, telling her to “go to bed. Don’t fight me,” according to an arrest affidavit filed in Collin County. The woman was smothered with a pillow into unconsciousness and robbed. However, paramedics revived her and she told investigators that her attacker had stolen a box containing her jewelry. Police identified Chemirmir from a license plate number and were able to find and tail him days later, when they watched him throw a jewelry box into a trash bin. They traced the box to Harris, according to the affidavit.

Plano police Chief Gregory Rushin said at the time that Chemirmir used his health care experience “to his advantage in targeting and exploiting seniors, some of the most vulnerable people in our community.”

Police said then that investigators were reviewing about 750 unattended deaths of elderly women for possible links.

Chemirmir’s attorney, Phillip Hayes, said Thursday that this week’s charges were a surprise and that he hadn’t had time to review them yet.

“These cases came out of the blue and I don’t have any information on them yet,” he said.

But he noted that Chemirmir “has denied it since Day 1” that he played any role in Harris’ death. “They have circumstantial evidence that puts him in the area but that’s as far as the evidence goes,” Hayes said.

In addition to the murder charges, Chemirmir is being held on a charge of being in the country illegally.