A Utah mother was arrested on suspicion of aggravated murder for the death of her 23-day-old baby.

Tawna Steed, 32, was booked into jail Monday in Beaver County after a police investigation found she allegedly shook her infant son on at least two occasions, causing his death. The baby’s father, Josh Downey, told police she was yelling “stupid baby to stop crying.”

Probable cause court documents state she was “shaking the baby vigorously and grabbing it tightly across the chest with her two hands.”

A 911 call on Sept. 19 reported the baby was not breathing and efforts to revive him were underway. Medical personnel responded to an apartment on Main Street in Beaver to try to save the child. He was transported to the Beaver Valley Hospital where he was later pronounced dead and an autopsy was ordered.

Police interviewed Downey and Steed who told officers they were the only ones who had been with the child since he was born, except for one or two brief times, including a 10-minute trip to a grocery story.

The results of an autopsy were reported to police on Oct. 12, declaring that the manner of death was by homicide. The pathologist told police the infant had multiple healing rib fractures from injuries on at least two difference occasions.

According to the pathologist, the baby boy also had two separate brain hemorrhages and that could have been caused by blunt force trauma or by someone shaking the infant, causing his death.

Separately, Downey and Steed agreed to talk to police after they were informed of their Miranda rights. Downey told police he had not hurt his child and had not witnessed anybody else hurt him, including Steed.

“Josh was very emotional at times, crying and putting his head into his hands,” according to the documents. Police told Steed about the findings of the autopsy and she denied hurting or killing the child. She said the baby and his father had a wonderful relationship and said the Downey would never hurt or kill the baby.

Police told the mother that either she or Downey had not only hurt their child but one or both of them had killed him.

“Tawna never cried or became upset during the interview,” police wrote in the court documents. “Eventually Tawna asked for an attorney and was placed under arrest.”

After her arrest police spoke with Downey again and told him in detail the injuries his son suffered.

“Josh again became very emotional, crying and leaning over putting his head into his hands.”

Downey told police he saw the baby’s mother shake him on two separate occasions. The first time he said he walked into the apartment and saw her sitting on the bed holding the child out in front of her, facing away from her, shaking the baby vigorously.

He said the child seemed stunned but got better when he carried him outside and comforted him. He said on both occasions, he took the baby and went to his parents’ house.

Steed will be held without bail by order of the judge in Utah’s Fifth District Court in Beaver County.