A dreaded 'does anyone know anything about this incident' question..

I was in Italy this summer, and in a chapel on the island in the middle of Lake Iseo there is a painting of two twin-engined aircraft attacking the local ferry, apparently with machine guns. The local tradition is for family or friends to paint a picture of how someone buried in the grounds died, so the painting sits among many gruesome but I suppose theraputic renditions of car accidents (and even some earlier coaching accidents).

Because understandably the artist at the time wasn’t focussing on aircraft recognition points I have nothing to go on, but I am interested to know what happened at what is one of my favourite spots in the world. The artist, IIRC, said in a note underneath that they were ‘English’ aeroplanes – though the markings – two-colour roundels with a blue outer and white inner reminiscent of SEAC marks – might indicate glimpsed US white stars on blue.

This may not have been the entirely unnecessary attack on civilians it first appears – the area around the lake was heavily involved in war production – including the Caproni seaplane factory (I spent some time telling my not-very-interested girlfriend ‘I’m SURE that’s a seaplane hangar’ – to be vindicated on our return to my books). But the morality of total war is another debate. I’m sure the local populace didn’t see it that way.

Anyway, does anyone have any records that might match this incident? Sadly, there is no date on the painting. I am fully aware of how often people ask this kind of question (in a former life I was an aviation archaeologist, before we became largely extinct by law) – but this one is, perhaps, a little different.