The child was pronounced dead days after the incident, police said.
Police in Nassau County said the mother, previously nicknamed "Peaches" by investigators after a tattoo on her body, had been identified as a U.S. army veteran who was 26 at the time of the killing.
Two-year-old Julian is back to his playful self after a Madera County sheriff's deputy saved his life in March.
Heart-stopping video shows a toddler wandering into a busy street in Arizona, and nearly getting hit by passing cars before being rescued by a good Samaritan.
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The 14-month-old boy was "understandably shaken," but was not injured in the incident, police said.