An exchange of gunfire late Sunday night has sent one man to the hospital and a second man is being questioned by police.   According to the Milwaukee Police Department, the shooting incident occurred around 9:45 at N 40th Street and W Thurston Avenue.   The Police are investigating the incident where two men fired shots at each other.   A 25-year-old Milwaukee man was struck and is currently being treated at a local hospital for what are described as non-life threatening injuries.   A 19-year-old Milwaukee man who was also involved in the exchange stayed on the scene and is cooperating with Police investigators.   The younger man was not injured during the shooting.