When I have been reading Manga recently I have encountered many onomatopoeia words such as シャカシャカ as in 'Brush Brush' and パタパタ for 'rush rush/flap flap' but I have found some words such as シャッ for a 'zoosh/swoosh' sound but what is the 小さいつ (small tsu) ッ suppose to mean in this onomatopoeia when it is at the end of the word? for another onomatopoeia word, シャッ I read it as 'Sha'? but does the ッ change the way I pronounce the word in any way? Other examples of onomatopoeia words include しゃーっ 'shuum' and ボコッ 'thump'.
Sorry if the onomatopoeia words are wrongly translated. I just basically want to know what is the small 'tsu' (Hiragana or Katakana) do to the word when it is placed at the end because from my knowledge it usually indicates a pause for words like 学校【がっこう】.