They would fire once in that order, then start over for the second round.

The guard had fired once, but the light was bad.

Someone fired back at him once, and he recognized the shot.

Most of the times it's fired once, if at all.

I prefer the weapon you only have to fire once.

He fired once at a shape that suddenly appeared in his door.

At that point, he turned the gun on himself and fired once into his chest.

He fired once, from a distance of no more than a few inches.

Once fired, they lost their right to remain on the trading floor!

I think you will find that his pistol has been fired once.