UPDATE: 12:35 p.m. EST -- The American woman who was shot dead Sunday in her Kabul, Afghanistan, apartment was killed by a mullah, defined as a Muslim trained in Islamic law, CNN reported. The mullah was arrested, but the motivation behind the killing of Lisa Akbari — a dual U.S.-Afghan national who had been living in the Afghan capital for three years — was not immediately clear.

Details surrounding the investigation into the fatal events were also not available, according to a Kabul district police chief who did not provide the mullah's name. 

"We offer our sincerest condolences to her family and loved ones on their loss. We are providing all possible consular assistance. Out of respect for the privacy of those affected, we decline further comment," the U.S. Embassy in Kabul said in a statement after confirming the death.

Original story:

Lisa Akbari, an American citizen living in Kabul, was shot dead in her apartment Sunday night, NBC reported Monday. Akbari, a dual U.S.-Afghan national, had been living in the Afghan capital for three years, a senior police official told NBC News on condition of anonymity.

"We offer our sincerest condolences to her family and loved ones on their loss," a U.S. Embassy official told the news site. "We are providing all possible consular assistance."

The embassy did not offer details on the incident. A suspect was reportedly apprehended a few miles away.

Akbari reportedly worked as a research manager for the U.S. military from 2009 to 2013. She then worked for aid agencies, including World Vision, a Christian humanitarian organization. 

"R.I.P. to my beautiful older sister Lisa,” Mayana Aliah Akbari wrote on her Facebook page. “You were taken soon and very suddenly while in Afghanistan and this just feels like a living nightmare...I know God got back his Angel and is proud of you for all that you've done on Earth while you were still living. I promise the psychopath that killed you will have justice served to him."

The younger Akbari shared several pictures of her sister on her Facebook page. Afghanistan’s intelligence agency is now in charge of the investigation, a police official told NBC.

Afghanistan has seen surging violence in recent months. The Islamic State group, based in Iraq and Syria, has gained support and taken territory in much of the countryside. Earlier this month, Taliban militants detonated a car bomb and stormed a building near the Spanish Embassy in Kabul. At least two Spanish guards were killed in that attack.

A suicide bomber detonated himself at a U.S.-Afghan patrol near Bagram airbase Monday, killing at least five soldiers and wounding six others, according to the district’s governor, Abdul Shukur Qudusi. A Taliban spokesman claimed responsibility for the attack.