Evidence prosecutors plan to use in the trial of a young woman charged in the death of her own baby includes the woman's own statements that she killed the child, according to court documents obtained by Channel 4.

Alexandra Tobias, 22, is accused of shaking her 3-month-old son to death in January.

"He's only 14 weeks old; he's not breathing," Alexandra Tobias frantically told a 911 operator.

Shortly after that 911 call was made, Tobias told investigators a dog knocked her child off a couch, he hit his head and he stopped breathing. Court documents show that Tobias later admitted to shaking her baby violently because the 3-month-old would not stop crying while she was playing a game on Facebook.

Prosecutors said they also have a statement from a cellmate who says Tobias confessed to her.

"I asked her 'What you here for?' and she said, 'Murder,'" inmate Lois Hay said. "I said, 'Murder? Who who did you murder?' She said, 'I my murdered my baby, my own baby.' And I was, like, 'Why did you do that?' She said she shook her baby and during the shaking of the baby, the baby hit his head on the computer."

In recorded telephone calls Tobias made to family members, she said the recent death of her mother affected her psychological state, and it may have been a contributing factors to her aggression on the night of her son's death.

"Ever since I found my mother dead, I just haven't been the same," Tobias said.

Tobias is being held on charges including aggravated child abuse and murder. Pretrial in her case is scheduled for November.