A 92-year-old U.S. woman has been charged with killing her son because she believed he was going to place her in an assisted living facility.

Anna Mae Blessing told authorities she had been contemplating her 72-year-old son’s intention to send her away for several days because she had “become difficult to live with” before she confronted him, according to a press release by the Maricopa County Sheriff’s Office.

Police said Blessing grabbed two pistols, which she had owned since the 1970s, and hid them in the pockets of her robe on Monday morning. She then confronted her son in the master bedroom of the home they shared, along with the son’s girlfriend, in Fountain Hills, Ariz.

After an argument, Blessing fired several rounds at her son and killed him, authorities said. Court documents state that deputies discovered the son’s body on the floor with gunshot wounds to the neck and jaw.

Blessing then pointed her pistol at the son’s 57-year-old girlfriend, who had been hiding in the corner during the altercation, the document said.

The girlfriend was able to knock the gun from the senior woman’s hands during a struggle. Blessing then retrieved her second pistol and attempted to aim it at the girlfriend. The younger woman managed to wrestle that one away from her too and threw it away in the direction of the first pistol, according to the court document.

The girlfriend then ran downstairs and called police.

When deputies arrived at the home, they found Blessing sitting in her recliner and her son dead in the master bedroom.

As officers led Blessing out of the home, she spontaneously said, ‘You took my life, so I’m taking yours,’” the court document said. Authorities later determined in an interview with Blessing that she believed her life was being taken by her son and his girlfriend because of their intention to put her in an assisted living home.

Blessing also told police that she had intended to kill herself, according to court document. She also said she should be “put to sleep” for her actions.

The son’s girlfriend told authorities Blessing had been living with them for six months before the incident.

Sgt. Bryant Vanegas of the Maricopa County Sheriff’s Office told local stations KPHO and KTVK that there had been other incidents at that home in the past, but he would not elaborate further.

“This is definitely an odd one,” he said. “There’s a lot of circumstances surrounding it of course, but it's definitely something you don't see every day and it's very unfortunate that this took place.”

Blessing has been charged with first-degree murder, aggravated assault with a deadly weapon, and kidnapping. Her bail has been set at US$500,000.

With files from CNN affiliates KPHO and KTVK.