My wife's family lives one kilometre away from where they were killed and know the family very well.
It is a tragedy that no one could have prevented this as there is a strong suspicion that it was encrusted with mud and looked like a rock of which farmers throw on the sides of fields.
All over this area there are arms dumps when the Germans fled in front of the advancing Russian army and my father-in-law found a dump on his farm three years ago and promptly called the army who disposed of it.
All the children in the area are having special classes informing them of the tragedy warning them not to touch suspicious objects; always smart to think of things in hindsight, but in this case it's a shame that this was not done before.
Some ordnance has labels like "warning", "danger", "handle with care", etc. Or this:
Don't be daft my friend as this ordnance maybe 70 years old and as I said it was covered in mud and any lettering would be virtually imposable to read, if it was there at all.