Hey,
If your sprite keeps playing, it is set to "Loop" - you can disable this in the animation setting bar to your left.
If you want to start an animation in your game on a given time, do like this:
[CONDITION] If something happens - [ACTION sprite] set animation to ""
You can also set the animation to loop and then stop the animation when you want; then the event ^ will look like this:
[CONDITION] If something happens - [ACTION sprite] set animation to ""
[ACTION] Wait X seconds - Stop animation
Its very simple but if this sounds advanced you should get another one to help you out better than me lol
Sry for bad english.