An Arizona woman admitted to killing her mother by smothering her with a pillow Monday afternoon, according to Scottsdale police.

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Holly Brennan, 46, of Scottsdale, was arrested and charged with first-degree murder, the Arizona Republic reported. According to police, Brennan asked a neighbor to call authorities and then told a dispatcher she killed her mother, 79-year-old Sharon Simmons, the newspaper reported.

According to Scottsdale police Sgt. Ben Hoster, officers found Simmons dead in a bedroom in an apartment she shared with Brennan, KNXV reported.

According to Scottsdale police, there had been a history of domestic violence between Brennan and her mother bu they did not elaborate, the Republic reported.

When questioned by police Monday, Brennan admitted she had smothered her mother with a pillow, according to KNXV.

"Responding officers then went inside the apartment and located an elderly female deceased on the bed," Hoster told the television station.

Mike Bennett, who lives in the apartment complex, told KNXV that Simmons was "a sweet lady," but Brennan was "a little sketchy."

Bennett said he was surprised to hear Brennan’s confession.

"They handcuffed her and sat her down on the ground, and then they wouldn't let me out that door because they taped it all off," Bennett told KTVT. "She said, 'I did it, I smothered her with a pillow,' and I'm like, 'Am I hearing this?'"