MANSFIELD, TEXAS (CBSDFW.COM) — The North Texas woman accused of murdering her 9-year-old niece last month, smothered her with a pillow while she laid on top of her, according to the affidavit.

Around 12:30 p.m. July 27, Mansfield officers responded to a cardiac arrest call at a home in the 4200 block of Eagle Drive, where they found Melodi Sneed, 9, unconscious in the home’s game room. Melodi was shortly transported to Mansfield Methodist Hospital where she was pronounced dead.

READ MORE: US Supreme Court To Consider Controversial Texas Abortion Law

In the affidavit, one of the responding officers stated that Melodi’s 13-year-old cousin witnessed her being suffocated by his mother, 42-year-old Mercia Sneed.

Mercia and her son were then sent to the Mansfield Public Safety Building so detectives could conduct a forensic interview.

Police said Melodi’s cousin stated he saw her kicking her legs and attempting to scream, while his mother laid on top of her until she stopped moving.

READ MORE: Texas Mother And Son Arrested In Wyoming For Murder In Oklahoma

Mercia told detectives during an interview that she grabbed a pillow, walked over to Melodi — who was asleep on a coach — and put the pillow over her face to smother her. She said she pushed the pillow down on her face for two-to-three minutes and laid on top of her while doing so.

The affidavit said she attempted to clean Melodi’s face with peroxide, and then hid both the pillow and peroxide bottle.

A motive for the murder was never mentioned.

Mercia was arrested four days after the murder on July 31 and was charged with injury to a child and causing serious bodily injury.

MORE NEWS: Southlake Ranks 20th 'Best Small City In America'; Keller & Flower Mound Most Affordable

She is currently facing a capital murder charge and remains in the Tarrant County Jail.