The incident happened at around 6 p.m. Thursday, Jan. 25, in Farmingdale near Fulton and Williams streets.
Nassau County Police said Brandon Barnes, of West Babylon, was driving westbound on Fulton Street when he struck a 52-year-old male bicyclist traveling westbound.
The victim was knocked off his bike and suffered head trauma. He was taken to a hospital.
Following the crash, Barnes allegedly fled the scene but returned a short time later and was arrested.
An investigation found that he was driving under the influence of alcohol, police said.
Barnes is charged with DWI, leaving the scene of an incident, and third-degree assault.
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