We had a play where the other teams center was very slow at snapping the ball. Once the center began the snap my nose guard pulled the ball out of his hands and fell on it. A flag was thrown against the offense for an illegal snap. They walked off 5 yards against the offense and re ran 1st down. Being that I have never saw an illegal snap penalty I asked for clarification and the official replied that he didn't know and that the other official called it. I was then told that they would flag us if we grabbed the ball away from the center as that was against the rules. I always thought that the ball was live once the center initiated the snap. This was an under center snap in 3rd grade and not a deep snap. 

Penalty would be on the defense there no matter the grade as CoachemUp said. 
What grade was this in?