Well, I think there is too little information in the article for anyone to form an informed opinion.
Scenario 1: Mother and son enter supermarket. Child sees railing and makes a run towards it, with mother shouting at him / hurrying after him to come back. Kid swings on the railing, which immediately gives way, ending in him hitting his head and sadly passing away. Supermarket is aware of broken railing and has done nothing to warn customers about it, or fix it.
Scenario 2: Mother tells kid to go play somewhere so she can do shopping in peace. Kid treats supermarket like his personal playground, slips whilst swinging on a rail, hits his head and dies. Nothing previously wrong with the rail.
From the information given, both are possible, and both paint a very different picture. Scenario 1 would justify a lawsuit because the supermarket boss has opened his doors to the general public whilst knowing that his shop is a possible danger (not just to energetic kids swinging, but also to anyone who leans against the railing). Scenario 2 lays the blame fully on the parents.
The point is, we don't know the facts, so we can't factually state 'it's the parent's fault, they should have been watching their child'. Opinions are a different matter, of course, but it IS relevant to know what state the railing was in etc if you want to comment meaningfully. Just wanted to explain what I meant in my previous reply.
RIP kiddie.