The Brown's were not invited to view the Basement Tapes, they forced their way into the viewing and instead of upsetting the other parents already there (whose children were actually murdered by Dylan and Eric) they let them watch them instead of causing a big scene.
Brooks may have talked to Eric, there were witnesses who say they did see Brooks walking down the street moments before the shooting started, but whether he talked to Eric or not, there is no witnesses to that.
Brooks has openly admitted to being a liar, so take everything he says with a grain of salt.
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“And may you grow to be proud
Dignified and true
And do unto others
As you'd have done to you”