Citing in two connected sentences
Read what you have written, and check. Altering the order of punctuation and citation might seem a logical way to do it, but many style guides actually impose the respective order of those elements, and not logic.

In the end, I'm afraid you have to choice of either:


accepting ambiguity of your example
using the author's name to make things clear: “Twit et al. demonstrated that […]. As a consequence, it is categorised as X, Y or Z [Mr. Twit, 2013]”