You don't remember? - What? - Hitting him?

[Topstudent]

A guy is lying unconscios on the ground.

A: What happened?
B: You don't remember?
A: What?
B: Hitting him? / That you hit him?
A: What?
B: I'm just kidding. How drunk are you?

What would be natural here? And is the question mark OK?

 

[emsr2d2]

A guy is lying unconscious on the ground.

A: What happened?
B: You don't remember?
A: What?
B: Hitting him/That you hit him.
A: What?
B: I'm just kidding. How drunk are you?

What would be natural here no question mark here and is are the question marks OK?

You can use either "Hitting him" or "That you hit him" but both would end with a full stop, not a question mark.