The RO is definitely at fault. The RO should be the last person to move up range, not bullshitting with the previous shooter. Snowfence walls are a much better set up than those paneled ones. Not only for visibility, but they are less affected by wind.
While the RO absolutely ****ed up bigtime, in the end the competitor is responsible for every bullet that comes out of their gun. This video is the reason why when I'm competing I will always double-check the range to make sure nobody is on it when it's my turn to shoot. If there's solid walls that means I'll crouch down and look for feet. I don't want my only defense to be "the RO was supposed to check!"