The vacuum cleaner salesman was definitely at the wrong place at the wrong time bu it wasn't at the Gemini Club.

It was during the time in which Chris Rosenberg (and probably other members of the crew) had ripped off and murdered some Cuban drug dealers and their associates) Unfortunately for the crew some of the Cubans' friends had Chris' name and had pretty swiftly worked out just who Chris worked for. They demanded Chris' death as a weregild and threatened retaliation if it wasn't handled soon. So between the time that this happened and the time that he murdered Chris, Roy was very paranoid and on edge.

So when a eighteen year old of Puerto Rican/Italian descent dressed in suit and tie stopped his car outside of Roy's house, likely to get his bearings , Roy assumed the worst. He and his friends approached the car. The kid saw the men with guns and took off. They chased him down and murdered him.