The ultimate responsibility lies with the RO holding the timer. When that guy is me, if the stage has a complicated barrier arrangement like that one, after scoring I head to the back of the bay where I can see behind every one of the barricades and make sure I'm the last guy out.
But the guy downrange also needs to look himself in the mirror and ask:
-Why was there 10 seconds of shooting on his own bay that went unnoticed by him? There is a serious volume difference on your bay vs. even the ones right next door. If he's double plugged and that is the reason (which I doubt)... he needs to go to single protection. You need SOME hearing at a practical shooting match, to hear RO commands, etc, and e
specially gunfire on your own bay.
-If you are taping targets and look around and you are the only guy you can see, chances are it is time for you to yell "paster help" or something to let people know you are downrange and the stage isn't reset. If you are the only guy down range for the length of time that it takes for everyone else to be up range, have the next shooter make ready, and start shooting, and didn't think anything of being down range all by yourself for that amount of time, it points to the same root issue as the first one:
The guy downrange is suffering from a dangerous lack of situational awareness and doesn't need to be there either.
Luckily no one was hurt... this is EXTREMELY rare, as there are millions of stages run every year in practical shooting competitions, and few people have ever seen anything like this in person. It is a one off situation that hopefully will remind others to pay attention to what is going on around them, whether they are holding the timer or not.