Some info on shot patterns etc
Info on 28 ga shot.
One of many sites with copies of the official report, indicating the type of shotgun involved, a Brescia Perazzi.
This model can have various chokes, so it's hard to say what the exact pattern would be, but a 28 gauge is designed to spread the shot out quickly and at 30 yards the pattern would have been wide and those 262 pellets would have slowed down a lot.