[oXygen-user] interrupting and restarting an external tool script

I use bash scripts to run validation tests and build artifacts (I have an external tool called "build" that simply starts the bash script that has focus in the editor). I have noticed that if I start a script when another is running, there will be a failure of the first script, but then I am unable to successfully start any other script. It will return with error code 0, but not actually do anything. Is there a clean way to kill a script that is started in this fashion? Thanks, Tara