The man accused of firing a gun and killing two people at a Detroit Lions tailgate last Sunday will NOT be charged with a crime ... as officials say he was acting in self-defense.
The shooting took place in Eastern Market -- just blocks away from Ford Field -- as people were partying after the Lions had just lost a heartbreaker to the Tampa Bay Buccaneers.
Cops said a preliminary investigation revealed that 25-year-old Jalen Welch had gotten into a dispute with a 40-year-old man at the venue ... when the man opened fire and killed him.