Hopefully, a DC would go to him and "ask", so he could come to you again.
If not, as an on field "trainer", take him aside and explain the problem of disadvantaging the defense, un-ringing the bell, etc. Yes, I would be proactive with a newbie, in spite of knowing we don't do that normally.
Eventually, he needs to let both coaches know he made a mistake; but can't get out of it.