A Lions fan lost his life on Sunday — after he was shot and killed during a party after Detroit’s home game against the Buccaneers.

Detroit Police say the man — who was in his 40s — had been at a tailgate at Eastern Market in downtown in the hours after the Lions lost a heartbreaker to Tampa Bay … when he got into an altercation with another man.

Cops say witnesses told them the two guys squared up as if they were going to fight — when, suddenly, the man’s opponent pulled out a gun and fired.

The guy was struck by bullets and died at the scene. Another person in the area was hit by the gunfire as well — and is currently in the hospital in critical condition, cops said.

Police told media members the suspect shooter — who’s in his 30s — is currently in custody.

A further investigation into the matter remains ongoing.

Police Chief James White said the whole situation was “ridiculous” … adding, “The biggest story that should have been told is the Lions lost and some people had a fight.”