Which of these suggestions are fine?

In writing, which of these suggestions are fine? Could you please comment on each?

He sees a shadow and starts firing his machine gun at it...

...Realizing it was just his own, he stops. (1)

...As he realizes it was just his own, he stops. (2)

...He realizes it was just his own, and stops. (3)

...He stops as he realizes it was just his own. (4)

...He stops, realizing it was just his own. (5)