Police say Romy Fabre, 26, entered the Hicksville post office on 185 West John Street on Monday around 4 a.m.
Authorities say he used a stolen USPS-issued master key to remove the contents of mail boxes.
When law enforcement officers attempted to take him into custody, they say he resisted and used a sharp object to slash a postal inspector in the face and body.
The suspected getaway driver, 22-year-old Jahki Hawkins from the Bronx, was also arrested.
The postal inspector was taken to the hospital for treatment for cuts to his eye, face, leg and arm.
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