It took less than five minutes, a mere 11 plays from scrimmage into the Hall of Fame Game, for the first lowering-the-helmet flag to fly in.
Baltimore Ravens LB Patrick Onwuasor was the culprit, and the transgression seemed fairly obvious. Chicago Bears RB Benny Cunningham's momentum had been stopped by Ravens LB Andy Levine, and that's when Onwuasor came to clean up the play. But he did so with his helmet down, not seeing what he was attempting to hit.
The new NFL rule states that "it is a foul if a player lowers his head to initiate and make contact with his helmet against an opponent.