"It is an isolated incident, and there is no threat to the public," Norwalk Police spokesman Lt. Terry Blake said.
Blake declined to say what the injury was or how it was inflicted, and he did not identify the victim.
An employee at Ink Side Out Tattoos at 47 Wall St, declined to comment later as he cleaned up a bloody area on the front door step of the business.
Wall Street was briefly closed to traffic during the police investigation.
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