It didn't really need vocalising in English because if the bad guys started shooting at the glass partitions everywhere, it would be obvious as to why they were doing so. The funny thing is it's all down to cinematic transactional formality. If it isn't explained to the audience it might equate to a partial dramatical vacuum, so it gets popped in one way or the other. We see McClane hopping around barefoot in the park and we already know the guy is going to be coming through. Also, I suppose it might have been done just so we could get a dose of Rickman's gruff accent (RIP) to fill that outright necessary space.