It is apparently unclear if the victim resisted or complied when the suspect demanded his newly purchased watch, but officers say he was shot in the upper back.
The victim was reportedly air-lifted to Nassau University Medical Center in East Meadow.
Police say the brother then tackled the gunman, who was able to escape.
Authorities say the suspect then got into a black car, possibly with Rhode Island plates. Three other men were allegedly in the car waiting.
