Zend certified PHP/Magento developer

Taskkill can’t end process but taskmanager can

I recently found out something interesting: I can’t kill tasks with taskkill but the Task-Manager kills them. I can end the process with the task manager just fine, but when I try it with taskkill, it gives me permission denied.

PS C:Usersuser> taskkill /PID 8640 /F
ERROR: The process with PID 8640 could not be stopped.
Reason: Permission denied

Anyone knows what is going on here and how to fix that problem?

PS: I know I can kill it with an administrative shell, but that is not the solution I am searching for. If the task manager can do it without permission, taskkill should do it as well.