Court records obtained by the AP show that Leonardo told investigators she left Aiden and his 23-month-old sister alone in the tub so she could have some "me time." She walked away for about 10 minutes.
During that time, she smoked a cigarette and listened to some music on her cellphone, a warrant states.
When she returned to the bathroom, Aiden was floating in the water and not breathing. Leonardo called 911.
His sister, identified by WBIR in Knoxville as Sophia Leonardo, was not hurt. She is in the custody of grandparents, the news station said.
The children’s father, David Brandon Dillingham, defended Leonardo Friday in an interview with WBIR.
"It was just an accident. Lindsey is not to blame for this," Dillingham told the news station. "She just made a bad judgement call, even though it was the wrong time, but she's a great mother and does anything and everything for our babies."
Court records obtained by WBIR paint a strained relationship between Dillingham and Leonardo, who do not live together. In May 2019, Dillingham filed for, but was denied, an order of protection against Leonardo.
Dillingham wrote in his petition that Leonardo would following him home and go to his workplace, where she “cusses (him) in front of (his) co-workers.”
WBIR reported that Dillingham was denied the order because the court found he did not prove his case.
In October, Leonardo filed a petition for a protective order against Dillingham.
“My relationship with David has been traumatic from the beginning,” Leonardo wrote in the petition, in which she accused Dillingham of threatening to harm Aiden and Sophia.
The court also denied her petition, WBIR reported.
Dillingham admitted that he and Leonardo “didn’t see eye to eye on things, and every relationship has its problems.” Still, he defended her against the murder charge filed by police.
He told the news station he is devastated over his son’s death.
"Please watch your children very closely. Every second counts," Dillingham said. "And you can't take anything for granted."