Tallahassee police said 23-year-old Te'Lea Jefferson is charged with murder and aggravated battery for the toddler's death.
According to the Tallahassee Democrat, Jefferson brought the unresponsive boy to the emergency room at Tallahassee Memorial Hospital at 6:58 p.m. with severe trauma to his head and face.
The toddler had a body temperature of 88 degrees when he arrived at the ER. He was pronounced dead six minutes later by hospital staff, who called Tallahassee police.
Jefferson told responding officers that the little boy was standing on the sink while brushing his teeth when he fell, WCTV reports.
She claimed he struck his head on the toilet, and broken pieces of porcelain caused cuts on the boy's body.
But the arrest affidavit said the toddler's injuries were not consistent with a fall, noting he had severe cuts on his face and hands, along with bruises on his arms and legs. There were also indications of older injuries on his torso and shoulder.
After police said her timeline of the events didn't add up, Jefferson reportedly admitted she attacked the boy because he wouldn't stop standing on the sink.
The arrest report said she threw the tire iron at him, and admitted to using it to hit the child several times, including after he tried to run away. She then told police she hid the tire iron outside of the home.
Police said she also believed that the little boy was likely already dead before she drove him to the hospital.
Investigators said Jefferson also admitted to physically punishing the boy before, telling officers he was stubborn and "often required more strikes or blows than his older sibling," the arrest report said.
The Tallahassee Democrat reports that Jefferson lived with the victim and his 6-year-old brother, both of whom had suffered abuse in the past. According to WCTV, she is in a relationship with the parent, and said she stayed home five days a week to watch the children while the parent went to work.
A judge ordered Jefferson to be held without bond. She is expected to appear in court again on Thursday.