Type "w" to find out what other user(s) there are, and what they are doing.
Then use "ps auxf" to display a tree of all processes, or "ps uxf" for your own processes.
Start looking for "bash" or something simular, because that's your shell.
Kill it: kill <processid>
* Copy-paste the processid, by selecting it, and pressing the middle mouse button.
If the process hangs, it won't respond to your "sigterm" signal; use "kill -9" instead; the kernel will clean up the process immediately.