[qno2]

Thought so too but... hey, I didn't want to go too much off-topic now.

In EP4: assuming that the grate is large enough for medium-sized objects to fall through it's just a pretty simple trick:

For example, attach something heavy to the gun with a rope (my english fails me here and I'm not a gun-expert to begin with... at the part of the gun that points towards the user), let the weight hang through the the grate; the weight should pull it down after you stop holding it - shoot.
Though there might be issues with the depicted distance between Shannon and the well.
Even easier: just stand above the well, look down right into the barrel... carries the risk that the gun might not fall through the grate or the body's placement being too obvious (too close).

Just like Kumasawa and Gohda in the same EP, looks like more than it actually is. In some other mystery novels you'd get some weird, convoluted structure that somehow made it possible to achieve the same thing. Especially in something like Detective Conan.

In fact, Nanjo and Shannon are - as far as I know - more less the only ones that could've pulled this one off, and Nanjo has this one nifty red about him and murder. I don't want to know how Rosa managed to fall on shotgun she killed herself with (if that is KNMs explanation), while still hitting her head with the bullet. Well, there is one exception though: anyone from "Kyrie's group" except for Kyrie could've hid the gun "somewhere in the woods" (another dumb trick: with remote fire... just block the trigger with a piece of wood that's attached to a line while a tree-branch exerts pressure on it... pull the line when ready; add more convoluted tricks to get rid of the line and wood), so here goes Krausstrice.

I just highly doubt that Ryukishi has used any such "complex" tricks for just this one thing because he never used any during the story. Or they were at least not necessary.