[varina davis]

The previous post is not asserting that the police knew anything of the kind;

Yes it is.... or it wouldn't have asked the following question.... it is asking why they would make up this detail.

[anatolfz]

I think it means: they said there was a gun because that's what they had been told; of course they couldn't have known for sure, not having been present at the time; yet why should they lie about having been told there was a gun?