っ, or "short tsu", isn't a sound effect or noise someone makes, it's a glottal stop in speech and/or used entirely for emphasis
Translating it as "tsutsu" is fundamentally wrong, even moreso that you removed the entirety of the squiggly line (tilde) which is there to represent the pause
"----...!!!" is more faithful, but I can understand when someone uses an actual sound like "KH...!" or "GUH...!" to represent a sudden stop in speech, since it's easier to understand for a western reader
Translating a glottal stop literally, however, isn't conducive to the narrative or the comprehension of the reader