It's never easy being an umpire at any age level in baseball. There is either parents yelling at you or fans booing and heckling you, but this first-base umpire might take the cake for one of the worst calls in baseball history.
The batter clearly swings at the pitch, but the home-plate umpire still checks down to the first-base umpire, who said the batter did check his swing.
The only explanation for a call like this is the umpire just wasn't paying attention at all.