Police responded to reports of a man yelling and cursing at children and elderly people and then began hitting people.
The suspect was identified as Troy Timberlake, 31, and was detained, police said.
Police said Timberlake was yelling and cursing at people as they walked by the gazebo at Church Square Park, including one woman who he also spit on.
When the woman turned to address the suspect, he reportedly punched her, followed her out of the park, and punched her multiple times, knocking her unconscious, police said.
Joelle Robertson said her nanny, who she calls "Bee," said the attack was unprovoked.
"She is such a positive person and she takes amazing care of my kids," Robertson said.
Bee was by herself when she was punched, but kids in the park were stunned after witnessing the crime, Robertson said.
"When he approached her he spit on her, they were asking why'd you spit on me and then he decided to knock her down and punch her," Robertson said.
Police said the man then approached another victim, and hit him on the back of the head near the playground.
Hoboken EMS arrived to treat the victims, and one victim was transported to the hospital for further treatment.
Timberlake was charged with aggravated assault, endangering an injured victim, child cruelty and refusal to submit fingerprinting, police said.
Police said the suspect was not a stranger to law enforcement or crime.
"In the last 13 months he had been arrested four times, at least 1 assault prior to that, originally came from Washington, D.C. but our police department has dealt with him several times," Kenneth Ferrante, Hoboken Public Safety Director said.
Residents in the city are wondering how a person with an extensive criminal background and personal issues roams the streets creating chaos.
"This was such a horrible thing that was not necessary that happened," Robertson said.
Police patrols have been increased around the park.
A GoFundMe has exceeded expectations to help pay for the nanny's hospitalization and recovery.
"She's recovering at home, she's still very swollen and in pain," Robertson said.
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