Nassau police arrested a Bay Shore man Saturday night after he allegedly robbed a Jericho home while wearing a mask and holding a gun -- then police also arrested one of his alleged victims, whom they said was in on the crime.

A Nassau County police news release said that about 10:24 p.m., Eric D. James entered a Forest Drive house through an unlocked front door and demanded cash of a 17-year-old youth and Ryan E. Diaz, 20. When the teen said he didn't have any money, James, 29, who was wearing a white mask, took a Rolex watch from Diaz and a bag containing a "brown leafy mixture" believed to be marijuana or synthetic marijuana, police said.

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James fled on foot, and police were called.

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A Nassau police canine officer responding to the call pulled over a 2003 Nissan Altima driven by James, who was seen speeding and passing stop signs on Birch Park Drive, police said. Police said they later determined Diaz, of Muttontown, was a co-conspirator in the robbery.

Both men were arrested without incident. No injuries were reported, and a handgun, a mask and a bag were recovered, police said.

James was charged with robbery, burglary, criminal possession of a weapon, criminal possession of a controlled substance, criminal possession of marijuana, and vehicle and traffic violations.

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Diaz was charged with robbery and making a false written statement. Both men were scheduled to be arraigned in First District Court in Hempstead on Monday.