An Arizona woman has admitted to smothering her 79-year-old mother with a pillow, police said.

Holly Brennan, 46, was arrested Monday at an apartment in Scottsdale that she shared with her mother, Sharon Simmons, for several years. After asking a neighbor to call the cops, Brennan allegedly got on the phone moments later and told a dispatcher she had just killed Simmons, police said.

Simmons was later found dead by responding officers in a bedroom inside the residence. Investigators said there was a history of domestic violence between the pair, as Brennan was arrested in 2017 over threats against her mom.

She admitted that she smothered her mother with a pillow,” Scottsdale police Sgt. Ben Hoster told KNXV.

In addition, Brennan told officers she “hated her mother,” cops said, but her exact motive is not yet known.

One of the woman’s neighbors also told the station that he saw Brennan — who he characterized as a “little sketchy” — confess to investigators at the scene.

“Then they put the cuffs on her and sat her down on the sidewalk,” neighbor Mike Bennett told the station.

“I couldn’t believe what I was hearing. It took a couple seconds for it to sink in, and I’m like, ‘Wow, she just admitted that!’”

Bennett told KSAZ that Simmons’ death has “just floored” him and other residents at the complex.

“She was just a sweet lady,” Bennett said. “The lady was just a beautiful older woman. Her daughter lived there, but she didn’t seem to be the friendliest.”

It’s unclear if Brennan, who will face first-degree murder charges, has hired an attorney.