The suspect, identified only as a 14-year-old girl, was charged with capital murder after she drowned Justice Hull shortly before 6 a.m. at an apartment on Westmoreland Road, Dallas police Maj. Robert Sherwin said.
"There is very little doubt that this investigation has revealed that this was an intentional act," Sherwin told reporters Monday afternoon.
He did not discuss a possible motive in the slaying, though he did say the suspect "allegedly called police."
Justice's mother is in jail and had requested that the suspect's mother care for the young girl. The suspect's mother was at work when the drowning occurred, Sherwin said.
The 14-year-old girl is being held at the Henry Wade Juvenile Justice Center, and Sherwin said she could be tried as an adult under Texas law.