Calhoun was shot once after being approached at the corner of South Seventh Street and 12th Avenue around 2:30 a.m. on Monday.
He was taken to University Hospital, where he died a short time later.
Information from witnesses led police to Hemphill at a relative's home located on Summit Avenue in Newark.
Hemphill has been charged with murder and weapons offenses. He is being held in the Essex County Jail in lieu of $500,000.
He is expected to be arraigned next week.
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