Richmond scored just six points in Tuesday's contest but drained the final shot of the game and gave East Carolina (23-12) their first post-season championship in school history.
Richmond had been 4-for-23 from beyond the arc in three games prior to Tuesday and got his chance to hit the winner after Weber State (30-7) tied the game on a free throw by Davion Berry with 17.5 seconds to play.
Miguel Perry led East Carolina with 23 points. The Pirates had four players in double figures.
Scott Bamforth led Weber State with 19 points, including four shots from 3-point range. Berry and Frank Otis chipped in 16 points apiece.
East Carolina led 42-35 at halftime in a game that included 10 lead changes and seven ties.