Authorities arrested 25-year-old Ramon Thomas, who is homeless, for sucker punching and taunting the little boy last month while the child was with his mother.
The boy and his mother were on a southbound G train on Saturday, March 24, approaching the Bergen Street station around 4:25 p.m. when he was assaulted.
The victim sustained bruising and swelling on the left side of his face. He was taken to NYU Langone Health Cobble Hill, where he was treated and released
Investigators say Thomas checked himself into a psychiatric ward two days later.
Detectives couldn't arrest or question him while he was hospitalized.
Officers arrested Thomas Thursday and charged him with assault.
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