[svandamme]

I would argue that an company is required to have sensible adults in their establishment who can manage such a situation.. That's their responsibility for a business with customer facing employees.

If such a "manager" would have been there, he would have taken charge and de-escalated the situation rather then allowing it to escalate like it did.

It's no different from a construction yard with heavy equipment.. If you do not ensure adequate management, the safety standards will drop, and sooner or later somebody will run over a coworkers with a digger or set down a 10 ton weight on top of somebody, and the hard hat won't be hard enough to protect him.

Will it have been the fault of the operator that was looking on his facebook/phone? defo!

But it's also the construction company's fault for not having had somebody around to keep safety standards in check..

People at the lower end of the work force will do stupid things if left on their own. That's a known fact.
So it has to be mitigated, clearly that didn't happen here, so there is part blame.