The death of a woman that occurred after firearm attacks on power substations caused a massive power outage last year has been ruled a homicide, newly released autopsy records show.

Karin Zoanelli, 87, was found unresponsive in her home in Moore County, North Carolina, on the night of Dec. 3, 2022, following the power outage, according to records released by the state's Office of the Chief Medical Examiner.

Zoanelli's husband told police his wife was having difficulty breathing that night and he woke up to find she had fallen on the floor of their Pinehurst home, according to the records. She died shortly after midnight on Dec. 4.

Her cause of death was due to cardiovascular disease, according to the autopsy report, which lists pulmonary hypertension as a contributing condition.

Zoanelli had chronic lung disease with pulmonary hypertension and at night used an oxygen concentrator, which the power outage disabled, according to the autopsy report.

"While the decedent succumbed to her pre-existing natural disease, preceding failure of her oxygen concentrator as a result of a power outage precipitated her demise through exacerbation of her breathing insufficiency," the autopsy report stated. "And since the power outage involved reportedly occurred in the setting of a criminal firearm attack on the regional electrical distribution substation, the manner of death is best classified as Homicide."

Roughly 45,000 utility customers lost power amid the blackout. Evidence of sabotage was found at two key electrical substations operated by utility provider Duke Energy, prompting the Moore County Sheriff's Office to investigate the incident as a "criminal occurrence" and call in the FBI to assist in the probe.

The county, state and Duke Energy are offering a $75,000 reward for information leading to the arrest and prosecution of those responsible for what the Moore County sheriff called "intentional vandalism."

The FBI Charlotte Field Office is also offering a $25,000 reward in the incident.

No arrests have been made in connection with the substation shootings.

Moore County Sheriff Ronnie Fields said following the attacks that if someone died as a result of the blackout, the suspect or suspects could face murder charges.

ABC News' Bill Hutchinson contributed to this report.