Just to avoid confusion, by p9 and p8 you refer to the two outermost long primaries, right? Here at birdforum most count the other way round (p10 = p1, p9 = p2, p8 = p3 ect.)... I will use the more common way of counting.
Judging relative lenght of primaries on a bird in motion is not reliable. If you look at your photos on some p2 appears significantly shorter than p3 in others not so much. We would ideally need a shot of the perched bird with slightly open wing. But agree that p2 appears to be rather long for Brown. Also concerning p1 - thanks for bringing this up Alexandre - it is long, but is it long enough? Same could be said for the outermost tail feather, is it short enough for a pure Brown?
I'm tempted to consider a hybrid Red-tailed X Brown Shrike... What do others say?