How do you tell a seven year-old that his mother and twin sister was in a car crash?

With a heavy heart after getting the phone call from the hospital the father looked at his son and asked himself that question over and over.

"Brad..." he stopped for a second. "Mom and your sister were in an accident and we need to go to the hospital too see them."
He hugged his son and Brad asked his father "What happened?"
"A horrible car crash happened" his father replied and his eyes started tearing up.

They got into the car and not a single word was spoken. They both sat there quiet for most of the drive when the dad broke the silence with
"You know that the body needs blood to survive"
"Yes?" said Brad quietly
The dad stopped the car and turned to his son
"Since you and your sister are twins you have the same blood and she has lost a lot of blood" The stopped for a second before continuing
"Would you want to give blood to your sister?"
Brad was quiet for a while before the looked his dad in the eyes and said a quiet
"yes..."
He looked at his dad and asked
"Will it hurt?"
"It will sting a little bit and the start but after that you wont feel a thing" His dad said with a smile while his eyes were tearing up

They drove the last few minutes to the hospital in silence and brad got sent with with the doctors to get him prepped for the blood transfer.
"Are you ready?" the doctor asked Brad and Brad nodded as his eyes started tearing up.
"What's the matter?" they asked him
"Will it hurt a a lot to give my blood to my sister?" he asked the doctor
"No, it will only sting a little bit and than its over" the doctor said with a smile on his face
"Ok" said Brad "Tell my sister that i loved her when she's getting better and that i will miss her when i'm gone"