Your example case is a little strange and without more context, I am not sure about the intent.
In general cases, just like Amanda said: it indicates a word being cut-off (or sometimes a very strong exclamation).
An interesting aspect is that it seems to work a little different from the equivalent in Western languages, in that it does not actually cut-off the word (in the text), but is added at the end. Let me illustrate...
If a comic book character was trying to say something, to be cut off suddenly (by another character, by a sudden event), the English would read something like:
What's happen... [cut to horrible monster devouring the hero]
the end of 'happen[ing]' being removed, is what indicates the abruptness of the cut.
The Japanese version would more likely be:
Both of which would be fully-formed words without the っ.
So, っ at the end of a word means something like "imagine the last mora of this word wasn't uttered", rather than "the rest of this word was cut-off", as a Westerner could be inclined to see it.