BOSTON (WHDH) - The mother of Bella Bond took the stand Friday in the murder trial against her daughter’s accused killer and ex-boyfriend, Michael McCarthy, saying that she saw him kill the girl before disposing of her body.

McCarthy is accused of killing the 2-year-old girl, whose body was found stuffed in a trash bag on a Deer Island beach in 2015.

WATCH: Rachelle Bond’s full testimony

Rachelle Bond described to the court the horrifying moment in which McCarthy allegedly punched the child to death inside her Dorchester apartment.

“He punched her in the stomach,” Bond told the court. “She was laying on the bed.”

Breaking down on the stand, the state’s star witnesses delivered chilling testimony as she described the night of the toddler’s death in June 2015.

“I just saw her bounce off the bed,” Bond said. “She bounced up and came back down.”

Bond told jurors that McCarthy punched the child in the stomach with great force, leaving her in an unresponsive state. Bond claimed to have tried CPR on her daughter but Bella did not respond. Bond said Bella’s head was “swollen and gray.”

Bond said after McCarthy killed Bella, he told her, “She just died. It was her time. She was a demon.”

Michael Sprinsky, a childhood friend of McCarthy’s, testified earlier in the week that the defendant “thought that he could remove demons from people’s houses.”

McCarthy felt as if Bella needed to follow stricter rules when it came to discipline, according to Bond. Bond said McCarthy would often lock Bella in the closet for being “fresh.”

After Bella’s death, Bond told the court that she did not flee the apartment because she was scared. She said McCarthy then grabbed her by the throat, threatened to kill her and then injected her with heroin. A day later, Bond said the pair went to dump Bella’s body. Bond said she saw a duffel bag in the backseat filled with weights and could tell Bella’s body was inside.

Bond said she confronted McCarthy later that day and when she told him he killed her daughter, she said McCarthy told her, “She was a demon. It was her time to die.”

Bond agreed to testify against McCarthy after making an immunity deal with prosecutors. She previously pleaded guilty to accessory to murder after the fact for allegedly helping McCarthy dispose of Bella’s body. She is slated to be set free upon conclusion of the trial.

The defense maintains that McCarthy was under the impression that Bella had been taken by the state. They plan to present a case that says Bond was the real killer.

For months, Bella was only known as “Baby Doe” as authorities struggled to identify her. A composite image of the girl was shared by millions on social media.

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