WEST ISLIP - It's been nearly three weeks since a man was killed in an apparent hit-and-run in West Islip, and police still have not made any big breaks in the search for the driver. However, police say they're investigating whether the victim, 27-year-old Jason Nelson, was involved in an altercation shortly before he was mowed down and left to die.As News 12 Long Island has reported, Nelson had left his girlfriend's Sandra Avenue home back on July 2 to buy a pack of cigarettes. When he didn't return, his girlfriend went outside to find him lying in the street. He died in her arms, according to Nelson's family.Investigators say it's not clear what the altercation may have been about or if Nelson knew the person he was arguing with before he was hit.Officials are offering a $5,000 reward for tips that lead to an arrest. Anyone with information is urged to call Suffolk Crime Stoppers at 1-800-220-TIPS.Police seek hit-and-run driver in fatal West Islip crashPolice try to track down driver in fatal W. Islip hit-and-run