[Inyo-Mono]

A misfire is when the round doesn’t go off.

Exactly, and how did two "rounds" go off accidentally while holding a single action revolver, which I assume they were using since it is a Western they're filming, unless it was cocked or dropped onto the floor twice?

[norcal joe]

and how did two "rounds" go off accidentally

It's been reported that a single projectile hit both people, by passing through the woman and then striking the guy. Which does sometimes happen.

[Governor Dinwiddie]

It was reported that a bullet passed through Halyna's body and then into the body of the man was injured in his clavicle. There was only one shot fired according to reports.

[Yaelle]

The victims were hit by one bullet.