What is the point?

There is no call, other than for clean underware.

The RO(and others) did not do his job, and might ought(ask) to be relieved.

This type of thing has happened before, and there is no logical reason for it . The bottom line is the CRO/RO did not do their job. Another part of the equation is the competitor needed to be more aware of his/her surroundings, if the squad isn't down range with you, you need to let somebody know you are still down range.
My call after a justified ass ripping, and appropriate garment cleaning would be to give shooter the choice to proceed or be put down the shooting order a place or two.

Well before that cookie monster from IPSC land weighs in with the right answer, I'll try to answer it the best I can.
Yell Stop !
Instruct the competitor in the box to place his/her hands on his/her head
Instruct the competitor down-range to clear the range
Have the second RO inspect down-range to assure that it is clear
Have the shooter in the starting box then unload and show clear and then
ask if he/she would like to restart right away or go to the end of the line.

Charlie, I waited 5 days but, given your excellent answer, you don't need me to weigh in. Well done, old son. Would you prefer chocolate chip or peanut cookies?

The only thing I'd say is that there's no need to automatically unload the guy on the line once the downrange area has been cleared, because the competitor on the line might be ready to continue. Cheers!

OK,

Stuff happens. It has happened and it will, but to answer the question, stop the shooter. Have him/her stand easy, no need to put hands on top of head, just stay with the shooter and tell him not to touch his gun (An aside here, if you have to tell him not to touch his gun, we have an entirely new problem here) Have another RO re-verify that the range is clear and then proceed to ask the shooter if he wants to stand down or shoot straight away.

Important point here is to manage the range better. As a general rule, when we don't have a clear view of the entire COF we will have the RO or CRO be the last person off the stage, he stands at the rear of the pit and clear the stage back to to the line. No one should be left behind this way. Alternately, before starting the shooter, take a quick walk around the props that are blocking your view. Each COF can present its own brand of problem here, but again, things can happen so take all possible steps to avoid them.

This is why we again as a general rule holler loudly, "Range Going Hot!" before the range commands are issued. It may not be legal and I am sure someone will mention that only the approved commands should be used. BUT this Courtesy/Warning helps to prevent exactly this situation from occuring.

This is exactly why I and my RO police the stage after pasting and resetting the course. The last man out from the stage exclaims "The stage has been cleared and set, next shooter to the line, please."

Part of being a RO is knowing where people are on the course.