The sister of a USPS carrier killed in the Saturday rampage said she was on the phone with her when she was fatally shot.

Rosie Granados said her twin sister, Mary, was near the end of her delivery route when they were chatting. That's when she heard Mary scream. She thought maybe her sister was bitten by a dog.

Unsure what was going on, Rosie drove along Mary's route.

"I went to help her out. And unfortunately, I did see her laying on the ground," she told CNN.

"It is the worst pain somebody can go through," Rosie added. "She was just part of my life, part of my whole world. She was taken away from me and my mother, my family."

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