How does Annemarie explain her sister's death to Ellen?

From the text:

"I think it was partly because of the rain. They said she was hit by a car. I suppose the streets were slippery, and it was getting dark, and maybe the driver just couldn't see," Annemarie went on, remembering. "Papa looked so angry. He made one hand into a fist, and he kept pounding it into the other hand. I remember the noise of it: slam, slam, slam."