I'm looking for a film

Old american film about very poor boy living with his grandmother. I remember that there was a storm and his grandma came into the sea and died, he was also holding cat at home in the same time(?) He was bullied at school and was only talking to one girl. Then there was a scene when he came to school with a gun and pulled it out on lunch time. He said sth like "that's how it feels" and probably shot that girl.