I will stop this second wind right dead in its track…!
It’s impossible to set the chain through the bathroom window, no matter what kind of device or tool you use.
That’s just too much distance for anything to be precisely managed.
I did say it was a pretty simple one, but not quite that simple.
And now, I think I said in the narration that the spear was pretty crudely made. You’d need a much more proper javelin to have any hope of throwing it with such force.
The killer didn’t throw the spear. The spear was directly thrust into the victim’s chest by someone standing behind him.
Naturally, the bathroom window is too far away to do that from.