I want to tell someone a piece of news.
A body bag with a dead man (in it) has been found.
Is it really necessary to say the highlighted part?
I mean the dead body was inside the body bag.
Can we leave out "in it"?
I agree "in it" would make clearer but if it was omitted I'd still take it to mean that the body was in the bag. Since body bags are meant to put bodies in, I'd assume the body was in the bag. This is just personal preference.