Two children who were allegedly killed by their mother in Colorado were found to have died from gunshot wounds, according to an autopsy report.
Kimberlee Singler, 35, is wanted in Colorado Springs for allegedly killing her daughter Elianna, nine, and son Aden, seven, before fleeing to the UK.
She was arrested by British National Crime Agency officers in December and is facing extradition.
Documents from the El Paso County Coroner reveal that the children had significant levels of doxylamine in their system, a substance often used as a sleeping aid.
The reports indicate that Elianna succumbed to a fatal gunshot wound to her head, along with cuts on her neck that contributed to her death, according to the BBC.
An additional autopsy report for her younger brother, Aden, notes that he died from a gunshot wound to the head.
In each report, authored by forensic pathologist Dr Megan Kliesner, it was found that both children had "potentially toxic levels of doxylamine in their femoral blood."
"Autopsy and investigation indicate that these injuries were incurred as a result of the deliberate actions of another person," the report added.
The case has raised questions in the US about how a suspect managed to leave the country while wanted for murder.
Singler is accused of murdering her daughter and son, as well as attempted murder and assault.
Police responding to a reported burglary at her home in Colorado Springs on December 19 found the children's bodies plus Singler and her 11-year-old daughter, who were both injured.
Initial investigations found that the emergency call was fake but Singler vanished, triggering a US-wide hunt.
The dead children were identified by their father Kevin Wentz as Elianna Wentz and Aden Wentz.
The former married couple had been embroiled in a legal battle over access to the children and over other issues, according to court filings.
Mr Wentz said in a statement that he and his former wife had been in a bitter custody fight for the past five years. They divorced in 2020.
Singler even accused him of child abuse but the allegations were dismissed by a court.
She successfully requested a temporary protection order against Mr Wentz in September, accusinghim of pulling a knife on her.
A second similar request in November was denied and Mr Wentz was not deemed a threat.
Singler is due to appear at Westminster Magistrates' Court on February 26 as she awaits her next extradition hearing.
