It's because he is afraid.
He's afraid of losing her.
He's already gone; I can't lose her, too. I can't lose her, too… I can't…
And it's because of this fear that he is hanging on desperately to her, clutching her shoulders, arms hooked under her arm pits, chin pressed down into the crook of her neck, a bit to hard for her liking.
But she doesn't say anything.
It's because she is afraid.
She's afraid of losing him.
I can't lose him, too…
And it's because of this fear that she is returning his embrace, fingers laced in his hair, whispering incoherent nonsense in his ear.
"I won't go… I won't go…"
You're not going to lose me.