A teenage girl and her boyfriend, also a teen, have been charged with murder in the fatal shooting of the girl’s mother, who was 36 years old.

Hannah Thomas, 17, and Richard Avila, 16, were each charged with second-degree murder and weapons charges in the killing of Ottilia Piros at her home in Greece, New York, last week, the Rochester Democrat & Chronicle reported.

The teenagers are residents of Arizona and were visiting Piros over the holidays, police said. They were stopped for speeding on Dec. 29 driving west through Saint Robert, Missouri, and police there decided to call the department in Greece to confirm that Piros had given them permission to use her car, the newspaper reported.

Police found a handgun in the car and say that ballistics analysis indicates it was the gun used in the killing.

Greece Police Chief Andrew Forsythe on Tuesday called the killing “egregious and sickening,” and said that the teenagers had shot Piros twice in the head. He did not speculate on a motive for the killing.

The two teenagers remain in custody in Missouri waiting transfer to New York. It was not immediately clear if the pair had attorneys to represent them.