A teenage girl from Arizona and her boyfriend have been charged with murder after the slaying of a 36-year-old woman last month. 

Ottilia Piros, the girl's mother, was shot and killed at her home in Greece, N.Y., in December 2020.

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Hannah Thomas, 17, and 16-year-old Richard Avila were reportedly visiting Piros for the Christmas holiday, local authorities said. 

Both have been charged with second-degree murder and second-degree criminal possession of a weapon, police said, according to the Rochester Democrat & Chronicle

Thomas and Avila are residents of Arizona. The pair were stopped by police on Dec. 29 in Saint Robert, Mo., for speeding in Piros' car.

After Thomas and Avila gave varied accounts of their trip and false information, officers decided to call the Greece Police Department to confirm that Piros had given them permission to use the car. 

It was at that point that Piros' body was discovered.

Saint Robert officers also found a handgun in the vehicle that ballistics analysis showed was the gun used to shoot Piros in the head.

Piros had previously called Greece Police, saying she had not heard from her daughter for several days.

Newly appointed Chief Andrew Forsythe told reporters in a news conference on Tuesday that the act was "egregious and sickening," though noting that he was not yet prepared to discuss a motive.

"This woman, who didn't deserve this, [was killed] over the holidays at the hands of her own daughter," he said. "Think about that and the manner that this occurred. Our hearts go out to that family, to their friends because it doesn't get much worse than that."

The murder, which Forsythe deemed an "execution," was the town's only homicide of 2020.

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WHAM reported Tuesday that Thomas also faces a tampering charge in Missouri, where the two are awaiting extradition to New York for arraignment.

It was not immediately clear if the teenagers had attorneys to represent them, according to the Associated Press.