SCOTTSDALE, Ariz. — Scottsdale police released the audio of the 911 calls from a woman charged with second-degree murder in the death of her mother at their Scottsdale apartment. 

Police said Holly Brennan asked her neighbor, Carmen Rivera, to call 911, telling her she needed police right away. Brennan said she asked Rivera to call police because her own phone was "screwed up."

At first, Brennan tells the dispatcher, "My name is Holly, and I need police here," but she refuses to say why when pressed for information. 

"And then she says, very sad looking, 'I don't want to talk about it,'" Rivera recalled in an interview with Team 12's Antonia Mejia. 

The first call ended shortly after Brennan handed the phone back to her neighbor and walked away. 

After Brennan asked Rivera to dial again, Brennan told the dispatcher she killed her mother the day before.

Dispatcher: "You said you killed your mom yesterday, so is she also in the house or...?"

Brennan: "She is in the house. She is in the bedroom."

Dispatcher: "And how did you kill your mom?"

Brennan: "I smothered her."

"She had a hard time saying it," Rivera said.

In the 911 audio, Rivera becomes audibly upset after the revelation.

"I just went into shock, and I said again, 'Lord, have mercy,'" Rivera told 12 News. "Because I know she needs help...Mentally, she's not well."

Responding officers said they found Brennan's 79-year-old mother, Sharon Simmons, in the bedroom with a pillow partially covering her face. 

According to court documents, Brennan told police she killed her mother because she "wanted her gone" and she "hated her."

Police said there have been incidents of domestic violence involving Brennan and her mother in the past. 

RELATED: Woman smothered elderly mother with pillow in Scottsdale, police say

Brennan said in 2017 she talked about killing her mother on social media, which resulted in a threats arrest, the court paperwork says. She also allegedly told police she sought treatment in 2018 as she was having thoughts of killing her mother.

When asked how long she had planned this, Brennan said she decided a few minutes before. 

After her mother was dead, Brennan walked to Circle K and bought some vodka for herself and gin for her mother, the court paperwork says. Detectives said she placed the bottle of gin on her mother's stomach.