Yes. You ask what safeguarding procedures have been put in place in order to ensure that this never happens again.
I'll add to what others have said about pupils wandering about.
I've already said that pupils were wandering around the building during my last supply stint. Not only were they bullying pupils, but one gang of girls was picking on a young male probationer teacher.
Many people are blissfully unaware of the problems which exist in some schools. I can't speak for the situation elsewhere in the UK, but in Scotland you need a strong HT who is prepared to stand up to the Local Authority. If you don't...
A pp has correctly stated that children now truant inside the building - it's much more fun that way: they can text their pals, arrange to meet up in the stairwells and loos, cause chaos...
Before I retired from my permanent post, we had a "school refuser" who came to school but wandered the corridors - an S1 pupil who had done this all through primary.
Our SLT informed us that we were to follow the Ed Psych's advice: let him be, don't confront but give "friendly gestures" to encourage him to come to class...
One day I looked through my classroom window (onto the corridor) to see this child perched on top of a balustrade with a sheer drop below him.
I was a middle manager at the time, so phoned the office to summon a depute.
When the depute started to spout the Ed Psych's nonsense to me, I said "Fair enough, but when that boy splatters all over the Street [the dining room/thoroughfare area below my room] it won't be the Educational Psychologist's name that's plastered all over the front page of the Daily Record."
Miraculously, it then became possible for the SLT to persuade that boy to enter a classroom.